GB980751A - Removal of acidic gases from gaseous mixtures - Google Patents

Abstract

Sulphur is obtained from a solution of hydrogen sulphide in a liquid dialkyl N-substituted aliphatic amide, such solution having been obtained in a process for removing hydrogen sulphide from hydrocarbon gases by contact with the dialkyl amide in a rectified absorption column, by introducing sulphur dioxide into the lower portion of the absorption column. Unabsorbed gases are washed in the upper part of the column to remove sulphur dioxide and precipitated sulphur is recovered from the absorbent.ALSO:Acidic contaminants, such as hydrogen sulphide, sulphur dioxide, carbonyl sulphide and carbon dioxide, are separated from hydrocarbon gases by countercurrent contact in a rectified absorption column with a liquid dialkyl N-substituted aliphatic amide; the gas is simultaneously dried by the absorbent. Specified absorbents are dimethyl, methylethyl, diethyl, propylmethyl and dibutyl formamides, dimethyl and methylethyl acetamides and dimethyl propamide. The gas may be a flue gas, refinery gas or natural gas containing 3-90% mol. of hydrogen sulphide. The absorption column is preferably operated at above 14 kg./cm.2 abs. and 10-65 DEG C. with the bottom temperature 20-80 DEG C. higher than at the top of the column. The maximum ratio of hydrocarbon and hydrogen sulphide in the solution should be 5 : 100 parts by weight. The absorbed gases may be recovered by flashing at 0.45-7 kg./cm.2abs. and simultaneously or subsequently stripping by heating and, if desired, with a stripping aid such as a C4-C12 hydrocarbon oil. The stripped gases are washed with a C12-C18 hydrocarbon wash oil such as a gas oil to recover any gasoline hydrocarbons, the washing being effected in the top of the stripping tower or in a separate tower.ALSO:Acidic contaminants, such as hydrogen sulphide, sulphur dioxide, carbonyl sulphide and carbon dioxide, are separated from hydrocarbon gases by countercurrent contact in a rectified absorption column with a liquid dialkyl N-substituted aliphatic amide; the gas is simultaneously dried by the absorbent. Specified absorbents are dimethyl, methylethyl, diethyl, propylmethyl and dibutyl formamides, dimethyl and methylethyl acetamides and dimethyl propamide. The gas may be a flue gas, refinery gas or natural gas containing 3-90% mol of hydrogen sulphide. The absorption column is preferably operated at above 14 kg./cm.2 abs. and 10-65 DEG C. with the bottom temperature 20-80 DEG C. higher than at the top of the column. The maximum ratio of hydrocarbon and hydrogen sulphide in the solution should be 5:100 parts by weight. The absorbed gases may be recovered by flashing at 0,45-7 kg./cm.2 abs. and simultaneously or subsequently stripping by heating and, if desired, with a stripping aid such as a C4-C12 hydrocarbon oil. The stripped gases are washed with a C12-C18 hydrocarbon wash oil such as a gas oil to recover any gasoline hydrocarbons, the washing being effected in the top of the stripping tower or in a separate tower.