US 2014/0234176 A1Published application

Simultaneous High Efficiency Capture of CO2 and H2S from Pressurized Gas

AssigneesSRI International, EIG, Inc.

InventorsEli Gal, Gopala N. Krishnan, Indira S. Jayaweera

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Abstract

Low-cost and energy-efficient C02 and H2S capture is provided obtaining greater than 99.9% capture efficiency from pressurized gas. The acid species are captured in an ammonia solution, which is then regenerated by stripping the absorbed species. The solution can capture as much as 330 grams of C02 and H2S per 1000 gram of water and when regenerated it produces pure pressurized acid gas containing more than 99.7% C02 and H2S. The absorption of the acid species is accomplished in two absorbers in-series, each having multiple stages. More than 95% of the acid species are captured in the first absorber and the balance is captured in the second absorber to below 10 ppm concentration in the outlet gas. The two absorbers operate at temperatures ranging from 20-70 degrees Celsius. The two absorbers and the main stripper of the alkaline solution operate at similar pressures ranging from 5-200 bara.

Claims12

Dependent claims

A system for a multi-staged capture of CO2 and H2S from a pressurized gas stream producing a clean pressurized gas stream containing less than 1 ppm H2S and less than 10 ppm CO2 and achieving greater than 99.9% capture efficiency, wherein the pressure in said pressurized gas stream and said clean pressurized gas stream is above atmospheric pressure, comprising:

(a) an alkaline solution containing 5-15 molal NH3;
(b) a first multistage absorber for absorbing CO2 and H2S from said pressurized gas stream combined with said alkaline solution, wherein greater than 95% of said CO2 and H2S content of said pressurized gas stream is captured in said alkaline solution, wherein a net loading of 110-330 grams of said CO2 and H2S per 1000 grams of water is absorbed in said alkaline solution;
(c) a second multistage polishing absorber using water for capturing the residual of CO2 and H2S in said pressurized gas stream entrained from said first multistage absorber and NH3 entrained from said first multistage absorber resulting in a gas outlet stream from said second multistage polishing absorber containing less than 10 ppm CO2 and NH3 and less than 1 ppm H2S.
(d) a main stripper for stripping said CO2 and H2S absorbed by said first multistage absorber in said alkaline solution, resulting in:
(i) a pure gas stream exhausted containing greater than 99.7% CO2+H2S, less than 0.3% water vapor and less than 10 ppm of each of H2, CO, NH3 and CH4, and
(ii) said alkaline solution reduced of said stripped CO2 and H2S which is sent back from said main stripper to said first multistage absorber.
(e) a sour water stripper for stripping said CO2, H2S and NH3 absorbed by said second multistage polishing absorber in said water, and said water stripped of said CO2, H2S and NH3 is sent back from said sour water stripper to said second multistage polishing absorber.

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Dependencies are inferred from the claim text.