GB972140A - Removal of acidic gases from gaseous mixtures - Google Patents

Abstract

A gas containing hydrocarbons, e.g. natural, refinery or flue gas is purified to remove acidic gases, e.g. H2S, CCS or CO2, by contact with a liquid mixture of (a) an amine having a basic dissociation constant pKb at 25 DEG C. of 3-14, and (b) an aliphatic carboxylic acid amide, a cyclotetramethylene sulphone or derivative thereof and/or a perhalocarbon. The liquid absorbent may comprise by weight, 7.5-70% of amine, e.g. ethanolamine, diethanolamine, di-isopropanolamine, dimethylamine, methyl ethyl amine, phenyl ethyl amine, 2,4-phenylene diamine or methoxy ethyl diamine, the balance being constituent (b) and if desired up to 15% of water. Constituent (b) may be sulpholane, containing up to 4 alkyl substituents if desired, dimethylformamide, methyl ethyl formamide, diethylformamide, propyl ethyl formamide, dibutyl formamide, dimethylacetamide, methyl ethyl acetamide, formamide, acetamide, perfluoro ethane, perfluoro butane or perchloro propane. The contact is effected in a countercurrent absorber at 7-70 kg./cm.2 absolute and 25-135 DEG C. The absorbent is recovered by removing acidic gases by stripping at 112-190 DEG C. and 1-3.5 kg./cm.2 absolute. If preferred the absorbent may first be subjected to flashing, e.g. at 1.15-8 kg./cm.2 abs. and gasoline hydrocarbons may be recovered from the gases so released by absorption in a sponge oil. Part of the absorbent after flashing may be recycled without further stripping to the absorption column. Preferably part of the stripped absorbent, e.g. 1-4% of the total, is dried by stripping and returned to the absorption column above the point of entry of the main absorbent to dry the gas. Sulphur is obtained from hydrogen sulphide recovered from the absorbent by the Claus process or alternatively sulphur dioxide is also passed into the absorption column where it reacts with the hydrogen sulphide to give sulphur recovered as a solid in the absorbent.ALSO:A gas containing hydrocarbons, e.g. natural, refinery or flue gas is purified to remove acidic gases, e.g. H2S, COS or CO2 by contact with a liquid mixture of (a) an amine having a basic dissociation constant pKb at 25 DEG C. of 3-14 and (b) an aliphatic carboxylic acid amide, a cyclotetramethylene sulphone or derivative thereof and/or a perhalocarbon. The liquid absorbent may comprise by weight, 7.5-70% of amine, e.g. ethanolamine, diethanolamine, di-isopropanolamine, dimethylamine, methyl ethylamine, phenyl ethyl amine, 2,4-phenylene diamine or methoxy ethyl diamine, the balance being constituent (b) and if desired up to 15% of water. Constituent (b) may be sulpholane, containing up to 4 alkyl substituents if desired, dimethylformamide, methyl ethyl formamide, diethylformamide, propyl ethyl formamide, dibutyl formamide, dimethylacetamide, methyl ethyl acetamide, formamide, acetamide, perfluoro ethane, perfluoro butane or perchloro propane. The contact is effected in a counter-current absorber at 7-70 kg./cm.2 absolute and 25-135 DEG C. The absorbent is recovered by removing acidic gases by stripping at 112-190 DEG C. and 1-3.5 kg./cm.2 absolute. If preferred, the absorbent may first be subjected to flashing, e.g. at 1.15-8 kg./cm.2 abs. and gasoline hydrocarbons may be recovered from the gases so released by absorption in a sponge oil. Part of the absorbent after flashing may be recycled without further stripping to the absorption column. Preferably, part of the stripped absorbent, e.g. 1-4% of the total, is dried by stripping and returned to the absorption column above the point of entry of the main absorbent to dry the gas.ALSO:A gas containing hydrocarbons, e.g. natural, refinery or flue gas, is purified to remove acidic gases, e.g. H2S, COS or CO2, by contact with a liquid mixture of (a) an amine having a basic dissociation constant pKb at 25 DEG C. of 3-14 and (b) an aliphatic carboxylic acid amide, a cyclotetramethylene sulphone or derivative thereof and/or a perhalocarbon. The liquid absorbent may comprise by weight, 7,5-70% of amine, e.g. ethanolamine, diethanolamine, di-isopropanolamine, dimethylamine, methyl ethyl amine, phenyl ethyl amine, 2,4-phenylene diamine or methoxy ethyl diamine, the balance being constituent (b) and if desired up to 15% of water. Constituent (b) may be sulpholane, containing up to 4 alkyl substituents if desired, dimethylformamide, methyl ethyl formamide, diethylformamide, propyl ethyl formamide, dibutyl formamide, dimethylacetamide, methyl ethyl acetamide, formamide, acetamide, perfluoro ethane, perfluoro butane or perchloro propane. The contact is effected in a counter-current absorber at 7-70 Kg./cm.2 absolute and 25-135 DEG C. The absorbent is recovered by removing acidic gases by stripping at 112-190 DEG C. and 1-3,5 kg./cm.2 absolute. If preferred the absorbent may first be subjected to flashing, e.g. at 1,15-8 Kg./cm.2 absolute and gasoline hydrocarbons may be recovered from the gases so released by absorption in a sponge oil. Part of the absorbent after flashing may be recycled without further stripping to the absorption column. Preferably part of the stripped absorbent, e.g. 1-4% of the total, is dried by stripping and returned to the absorption column above the point of entry of the main absorbent to dry the gas.