Deacidifying gaseous effluent, e.g. natural, synthesis or refinery gas, by treatment with liquid reactants and extractants in process allowing absorbent regeneration with low energy consumption

摘要

#CMT# #/CMT# A method for deacidifying gaseous effluent containing acidic compound(s) (I) involves: (a) contacting with reactant(s) (II) in liquid form to give gas depleted in (I) and a liquid fraction containing (I)/(II) reaction products and unreacted (II); (b) contacting the liquid with extractant (III) to give fractions depleted and enriched in the products; (c) recycling the depleted fraction to step (a); and (d) regenerating the enriched fraction to release gaseous (I) and give (II)/(III) mixture. #CMT# : #/CMT# A method for deacidifying waste gas containing acidic compound(s) (I) selected from hydrogen sulfide, mercaptans, carbon dioxide, carbon oxysulfide, sulfur dioxide and/or carbon disulfide involves: (a) contacting with reactant(s) (II) in liquid form to give an effluent gas depleted in (I) and a first liquid fraction containing (I)/(II) reaction products and unreacted (II); (b) contacting the liquid fraction with extractant (III) to give first and second liquid fractions depleted and enriched respectively in the reaction products; (c) recycling the first fraction from step (b) to step (a), as at least part of the treatment liquid; and (d) regenerating the second fraction from step (b) to release (I) in gaseous form and obtain a mixture of (II) and (III). #CMT#USE : #/CMT# The gaseous effluent to be deacidified typically consists of natural gas, synthesis gas, combustion fumes (e.g. from oil- or coal-fired power stations), refinery gas, Claus process tail gas, biomass fermentation gas, cemetry gas or blast furnace gas. #CMT#ADVANTAGE : #/CMT# The amount of energy required to regenerate the absorbent solution after loading with (I) is minimized. #CMT#DESCRIPTION OF DRAWINGS : #/CMT# The figure shows a schematic diagram of one form of the process. 1 : Gaseous effluent supply line 2 : Acid-depleted gas outlet line 3 : Acid-loaded absorbent outlet line 4 : Reaction product transfer line 5 : Reaction product outlet line 6 : Expanded gas transfer line 7 : Reaction product-loaded extractant outlet line 8 : Regenerated reactant outlet line 9 : Coabsorbed product-enriched gaseous stream outlet line 10 : Extractant transfer line 11 : Regenerated absorbent and extractant outlet line 12 : Released gas outlet line 13 : Transfer line to heat exchanger 14 : Outlet line from heat exchanger 15, 16 : Extraction solution supply lines 17 : Absorbent recycling line 18 : Absorbent supplementation line 19 : Extractant supplementation line 20 : Liquid absorption solution supply line BS1, BS2 : Separating flasks E1, E2 : Heat exchangers P1, P2 : Pumps RE : Regeneration column V1 : Expansion valve ZA : Absorption zone ZE : Extraction zone #CMT#ENVIRONMENT : #/CMT# Preferred Process: The mixture formed in step (d) is separated into a first stream enriched in reactant (II) and a second stream enriched in extractant (III), to be recycled to steps (a) and (b) respectively. Alternatively the effluent is contacted with the mixture formed in step (d). Steps (a) and (b) are carried out in respective first and second zones; or are both carried out in a contact zone, specifically a membrane contacter in which the gaseous effluent circulates in (i) a passage separated by a membrane from another passage in which (II) and (III) are circulated or (ii) first passage separated by a first membrane from a second passage in which (II) are circulated, itself separated by a second membrane from a third passage in which (III) are circulated. #CMT#ORGANIC CHEMISTRY : #/CMT# Preferred Materials: The reactant (II) is N,N-dimethyl-benzylamine (IIa), N-ethyl-benzylamine, 3-(octylamino)-propionitrile or 3-(tert. butylamino)-propionitrile. The extractant (III) is water, an ether, a glycol, an alkylene carbonate, a dialkyl carbonate, sulfolane or N-methyl-pyrrolidone. #CMT#EXAMPLE : #/CMT# A mixture comprising 10 vol. % carbon dioxide in nitrogen was contacted under atmospheric pressure at 40[deg]C with a two-phase liquid-liquid mixture containing 70 wt. % N,N-dimethyl-benzylamine (IIa) and 30 wt. % water. After absorption of carbon dioxide and separation of the liquid phase, analysis showed that the aqueous phase contained 92% of the product formed by reaction of (IIa) with carbon dioxide.