Process for separating carbonic acid gas from methane-rich gas

• US 4,581,044 A
• Filed: 02/21/1984
• Issued: 04/08/1986
• Est. Priority Date: 01/12/1982
• Status: Expired due to Fees

• Current Assignee: Seitetsu Kagaku Company Limited (Sumitomo Chemical Company Limited)
• Original Assignee: Seitetsu Kagaku Company Limited (Sumitomo Chemical Company Limited)
• Inventors: Uno, Masaru, Hiraoka, Masakatsu, Ihara, Satoshi, Tanabe, Takeo
• Primary Examiner(s): Cintins, Ivars
• Application Number:
  US06/581,208
• Time in Patent Office: 777 Days
• Field of Search: 55/25, 55/26, 55/58, 55/68, 55/73, 55/75, 55/76, 55/163, 55/389
• US Class Current: 95/96
• CPC Class Codes: B01D 2253/102 Carbon
• CPC Class Codes: B01D 2253/104 Alumina
• CPC Class Codes: B01D 2253/106 Silica or silicates
• CPC Class Codes: B01D 2253/108 Zeolites
• CPC Class Codes: B01D 2253/116 Molecular sieves other than zeolites
• CPC Class Codes: B01D 2253/25 Coated, impregnated or composite adsorbents
• CPC Class Codes: B01D 2253/308 Pore size
• CPC Class Codes: B01D 2256/245 Methane
• CPC Class Codes: B01D 2257/504 Carbon dioxide
• CPC Class Codes: B01D 2259/40037 with two sub-steps
• CPC Class Codes: B01D 2259/40064 Five
• CPC Class Codes: B01D 2259/402 using two beds
• CPC Class Codes: B01D 2259/403 using three beds
• CPC Class Codes: B01D 2259/4062 using six beds
• CPC Class Codes: B01D 53/047 Pressure swing adsorption
• CPC Class Codes: B01D 53/0476 Vacuum pressure swing adsorption
• CPC Class Codes: C02F 3/28 Anaerobic digestion processes
• CPC Class Codes: C12M 21/04 for producing gas, e.g. biogas digesters for manure with production of biogas A01C3/028, biological treatment of water, waste water or sewage C02F3/00, C02F11/02, preparation of natural gas or syngas C10L3/06, C10L3/10
• CPC Class Codes: C12M 47/18 Gas cleaning, e.g. scrubbers; Separation of different gases separating dispersed particles from gases or vapours B01D45/00; separation of gases or vapours B01D53/00; gas washing apparatus for laboratory uses B01L5/04
• CPC Class Codes: Y02C 20/40 of CO2
• CPC Class Codes: Y02E 50/30 : Fuel from waste, e.g. synthetic alcohol or diesel
• CPC Class Codes: Y02P 20/59 : Biological synthesis; Biological purification
• CPC Class Codes: Y02W 10/10 : Biological treatment of water, waste water, or sewage
• CPC Class Codes: Y10S 95/903 : Carbon

Abstract

A process for separating and recovering carbonic acid gas from a methane-rich gas containing the same by a pressure swing means comprising contacting the methane-rich gas with an adsorbent for carbonic acid gas at a high pressure to obtain a refined methane gas and then desorbing the carbonic acid from the carbonic acid gas-adsorbed adsorbent at a low pressure to obtain a substantially pure carbonic acid gas.

Claims

1. A process for separating and recovering carbonic acid gas from a methane-rich gas containing carbonic acid gas, comprising the steps of adsorbing said carbonic acid gas from said methane-rich gas with a carbon molecular sieve having a nominal pore size of 3.0-4.0 Å

as the adsorbent at a high pressure to obtain a refined methane gas, then desorbing said carbonic acid gas from the carbonic acid gas-adsorbed adsorbent at a low pressure, said methane-rich gas being maintained at a temperature up to 50°

C. during said adsorption and desorption steps, and recycling an initial portion of the deadsorbed gas to the step of adsorption, thereby increasing the rate of recovery of said refined methane gas, and simultaneously enhancing the purity of the deadsorbed carbonic acid gas, so as to obtain a substantially pure carbonic acid gas.

2. A process according to claim 1, wherein the methane-rich gas is a member selected from the group consisting of a methane fermentation gas and natural gas.

3. A process according to claim 2, wherein the methane fermentation gas is a biomass gas.

4. A process according to claim 1, wherein the high pressure used in the adsorbing step is in the range of from atmospheric pressure to 50 Kg/cm² ·

G.

5. A process according to claim 1, wherein the low pressure used in the desorbing step is in the range of 5 Kg/cm² ·

G down to vacuum.

6. The process of claim 1 in which the initial portion of the deadsorbed gas which is recycled is from about 50% to 70% of the whole of the desorbed gas discharged during the desorption step, said deadsorbed gas being recycled to mix with said methane-rich gas prior to said step of adsorption.

7. The process of claim 1 in which the nominal pore size of the carbon molecular sieve is about 3 Å

.

8. The process of claim 1 in which the methane-rich gas is maintained at a temperature in the range of about 0°

C. to 40°

C. during the adsorption and desorption steps.

9. A process for separating and recovering carbonic acid gas from a supply of methane-rich gas containing carbonic acid gas, comprising the steps of conducting in a supply conductor said supply of methane-rich gas to an adsorbing means, adsorbing said carbonic acid gas from said methane-rich gas in said adsorbing means with a carbon molecular sieve having a nominal pore size within the range of 3.0 and above but less than 4 Å

as the adsorbent at a high pressure to obtain a refined methane gas, then desorbing said carbonic acid gas from the carbonic acid gas-adsorbed adsorbent at a low pressure, said methane-rich gas being maintained at a temperature up to 50°

C. during said adsorption and desorption steps, and recycling an initial portion of the deadsorbed gas back to said supply conductor to mix with said supply of methane-rich gas prior to said adsorption step thereby increasing the rate of recovery of said refined methane gas and simultaneously enhancing the purity of the deadsorbed carbonic acid gas so as to obtain a substantially pure carbonic acid gas.

10. A process for separating and recovering carbonic acid gas from a supply of methane-rich gas containing carbonic acid gas, comprising the steps of conducting in a supply conductor said supply of methane-rich gas to an adsorbing means, adsorbing said carbonic acid gas from said methane-rich gas in said absorbing means with a carbon molecular sieve having a nominal pore size of about 3 Å

as the adsorbent at a high pressure to obtain a refined methane gas, then desorbing said carbonic acid gas from the carbonic acid gas-adsorbed adsorbent at a low pressure, said methane-rich gas being maintained at a temperature up to 50°

C. during said adsorption and desorption steps, and recycling an initial portion of the deadsorbed gas back to said supply conductor to mix with said supply of methane-rich gas prior to said adsorption step, thereby increasing the rate of recovery of said refined methane gas and simultaneously enhancing the purity of the deadsorbed carbonic acid gas so as to obtain a substantially pure carbonic acid gas.