Process for extracting acetylene from pyrolysis gases obtained by the thermal decomposition of hydrocarbons

摘要

PICT:0870737/IV (b)/1 Acetylene is recovered from pyrolysis gas, which has been freed of carbon black, tar, carbon dioxide, moisture and condensable hydrocarbons, by washing with kerosene at -10 to -40 DEG C. and under pressure to dissolve selectively higher acetylenes and unsaturated hydrocarbons other than acetylene and ethylene, selectively dissolving the acetylene in the remaining gas in anhydrous liquid ammonia at -10 to -70 DEG C. and under pressure and recovering the acetylene from the resultant solution. Pyrolysis gas is stored in gas holder 2, then washed with aqueous ammonia in tower 4 to remove carbon dioxide, mixed with methanol and cooled in cooler 5 to remove water and liquid hydrocarbons. The gas is contacted in tower 9 with kerosene, e.g. boiling between 175 and 225 DEG C. and having a molecular weight of 180, at 1-10 atmospheres. The solution is stripped to remove acetylene and ethylene which are recycled then further stripped of other gases before being returned to tower 9. Overhead gas from tower 9 is contacted with liquid ammonia in tower 20 at 1 to 10 atmospheres. By partial expansion and/or heating, ethylene and some acetylene is released in tower 27 and recycled. Acetylene is recovered in tower 30 and washed with water to remove ammonia. Part of the liquid ammonia is distilled to remove high boiling impurities before recycling.