US 4,449,994 AGranted

Low energy process for separating carbon dioxide and acid gases from a carbonaceous off-gas

AssigneeAir Products and Chemicals, Inc.

InventorsWilliam P. Hegarty, William P. Schmidt

Life of this patent

Estimating the term…

Loading patent…

Abstract

A process is disclosed for the separation of carbon dioxide and sulfide gases from oil shale retort off-gases, coal gasification off-gases, oxygen fire-flooding or carbon dioxide miscible flood enhanced oil recovery off-gases for recycle to a retort, gasifier or petroleum reservoir or alternately delivery to another process. The process separates the off-gases into an essentially sulfur-free fuel gas and an acid gas for recycle to such a retort, gasifier or reservoir wherein the off-gas is compressed if necessary and cooled to separate the two streams, the acid gas is expanded in an auto refrigeration step to provide the necessary process refrigeration and the acid gas is then recycled to such a retort, gasifier or reservoir. In the oil shale retorting and coal gasification applications, the gas' sulfur constituents are sorbed on spent oil shale particles or coal ash.

Claims23

Dependent claims

A process for separating a carbonaceous off-gas containing acid gases, such as:

carbon dioxide, hydrogen sulfide and carbonyl sulfide by separating said off-gas into an essentially sulfur-free fuel gas and a sulfur containing acid gas stream, comprising the steps of:
(a) compressing and after cooling an off-gas from an off-gas producing operation;
(b) removing any butane and higher boiling hydrocarbons from the off-gas of step (a) by absorption in lean solvent and drying the compressed and cooled off-gas to remove moisture from said gas;
(c) cooling the off-gas from step (b) against product gas streams in a heat exchanger;
(d) separating the cooled off-gas in a rectifying column without the use of an external solvent into an initial sulfur-free fuel gas stream as an overhead fraction and a carbon dioxide and sulfide stream as a bottom liquid fraction;
(e) expanding the initial carbon dioxide and sulfide stream in order to cool by autorefrigeration the initial fuel stream in a heat exchanger;
(f) separating said cooled fuel stream into a final sulfur-free fuel stream and a sulfur-free reflux stream that is reintroduced into the head of the rectifying column;
(g) further expanding the carbon dioxide and sulfide stream in an autorefrigeration cycle to provide additional refrigeration for the cooling of the off-gas in the heat exchanger of step (c);
(h) sending said CO.sub.2 and sulfides to a carbon dioxide utilizing process.

6 more elements

A process for separating a carbonaceous off-gas containing acid gases, such as;

carbon dioxide, hydrogen sulfide and carbonyl sulfide by separating said off-gas into an essentially sulfur-free fuel gas and an acid gas stream, comprising the steps of:
(a) compressing and aftercooling an off-gas from an off-gas producing operation;
(b) removing any butane and higher boiling hydrocarbons by absorption in lean solvent and drying the compressed and cooled off-gas to remove moisture from said gas;
(c) subcooling the off-gas against product gas streams in a heat exchanger;
(d) separating the subcooled off-gas into an initial fuel gas stream as an overhead fraction and an initial CO.sub.2 and sulfide liquid stream as a bottom fraction;
(e) expanding the CO.sub.2 and sulfide liquid stream in an auto-refrigeration cycle for the subcooling of the off-gas in the heat exchanger of step (c);
(f) extracting residual sulfides from the fuel gas stream by contact of the stream with a physical absorbent solvent which has a greater absorptivity for sulfides than for CO, CO.sub.2, fuel hydrogen or fuel hydrocarbons;
(g) regenerating the physical solvent in a distillation column to recycle lean physical absorbent solvent to the extraction step of (f) and to produce a second CO.sub.2 and sulfide stream;
(h) sending said expanded CO.sub.2 and sulfides of step (e) to a carbon dioxide utilizing process.

6 more elements

Dependencies are inferred from the claim text.