Method for separating carbon dioxide

Patent metadata

Field	Value
Publication number	US-10807036-B2
Application number	US-201815966441-A
Country	US
Kind code	B2
Filing date	Apr 30, 2018
Priority date	Oct 29, 2015
Publication date	Oct 20, 2020
Grant date	Oct 20, 2020

Abstract

According to the present invention, in separating carbon dioxide by a membrane separation with a separation membrane system using an inorganic separation membrane from a mixed gas containing methane and carbon dioxide, and then by an acid gas removal process using an absorbent, by specifying the suitable range of the carbon dioxide mole fraction at the outlet on the carbon dioxide non-permeation side XCO2 in the membrane separation, which corresponds to an ideal separation factor of the inorganic separation membrane, the proper distribution conditions become feasible. As a result, a method for separating carbon dioxide in which the decrease of the production amount by methane permeation in the membrane separation and the energy loss accompanying the decrease are suppressed, and further the energy consumption in an acid gas removal process using an absorbent, which is a post-process, can be suppressed, is provided.

First claim

What is claimed is:

1. A method for separating carbon dioxide, comprising:
separating carbon dioxide from a mixed gas containing methane and the carbon dioxide, wherein
in separating carbon dioxide by a membrane separation using an inorganic separation membrane that is permeated by the carbon dioxide preferentially from the mixed gas, and then by an acid gas removal process using an absorbent,
a carbon dioxide mole fraction at an outlet on a carbon dioxide non-permeation side X CO2 of the membrane separation, corresponding to an ideal separation factor α of the inorganic separation membrane in the membrane separation, is expressed in the range surrounded by data points a 1 , a 2 , a 3 , a 4 , a 5 , a 6 , a 7 , and a 8 in a graph of α versus X CO2 ,
wherein α is an ideal separation factor of the inorganic separation membrane and is a ratio (α=K _CO2 /K _CH4 ) of the permeance of carbon dioxide (K _CO2 )(mol/(m 2 ·Pa·s) to the permeance of methane (K _CH4 )(mol/(m 2 ·Pa·s), X CO2 is a carbon dioxide mole fraction at an outlet on a carbon dioxide non-permeation side of a membrane separation using an inorganic separation membrane, and X CO2 is expressed by the following Formula (I) with a carbon dioxide non-permeation side pressure P X [MPaA] and a carbon dioxide permeation side pressure P Y [MPaA] in the membrane separation,
[Mathematical Formula 1]
X CO2 =A·P R +B   (I)

wherein P R indicates P Y /P X , each of A and B in Formula (I) is a value shown in the following Correspondence Table of A and B, corresponding to each ideal separation factor α of a 1 , a 2 , a 3 , a 4 , a 4 , a 6 , a 7 , and a 8 ,

wherein a range of the ideal separation factor α of the inorganic separation membrane in the membrane separation is 50 to 200

TABLE 1

(Correspondence Table of A and B)

α
A
B

a 1
50
0.7452
0.1593

a 2
50
0.7273
0.0751

a 3
80
0.7986
0.1059

a 4
80
0.7566
0.0493

a 5
120
0.8314
0.0732

a 6
120
0.7641
0.0314

a 7
200
0.8614
0.0476

a 8
200
0.7689
0.0181.

2. The method for separating carbon dioxide according to claim 1 , wherein
in obtaining a carbon dioxide mole fraction of 0.03 or less in a gas after separating carbon dioxide by the acid gas removal process using an absorbent,
in the range of P X from 2.10 to 6.10 [MPaA], and
in the range of P Y from 0.10 to 0.25 [MPaA].

Assignees

• Mitsubishi Chem Corp

Inventors

• Kawazuishi Kenichi
• Iwamura Masayuki

Classifications

• B01D71/0215

  Silicon carbide; Silicon nitride; Silicon oxycarbide · CPC title

• B01D53/228

  characterised by specific membranes · CPC title

• B01D69/02

  characterised by their properties · CPC title

• Y02C20/40

  of CO2 · CPC title

• C10L3/104

  Carbon dioxide · CPC title