SEPARATION AND PURIFICATION OF THERMALLY CRACKED GAS OF HYDROCARBON

摘要

PURPOSE:To eliminate the necessity or memarkably reduce of the amount of a refrigerant, by using, a stream of a gas-liquid mixed phase formed by depressurizing and expanding ethylene . ethane fraction separated in a demethanization step as a refrigerant, compressing the stream and introducing the compressed stream into an ethylene separation step. CONSTITUTION:A thermal cracked gas of a hydrocarbon is cooled in a cooling step 1 and part or all of the resultant condensate is fed to a demethanization step 2. Bottom liquid consisting essentially of ethylene . ethane from a demethanization column (T-1) is fed to plural expanders (V-1)-(V-3), depressurized and expanded to a pressure below the operating pressure in the ethylene separation step to provide a gas-liquid mixed phase stream at a low temperature, normally -80--90 deg.C. The above-mentioned mixed phase stream is then fed to heat exchangers (E-2)-(E-4) for cooling in the cooling step 1 and used until the stream becomes saturated vapor or superheated vapor. The resultant vapor is then compressed in a compressor (C-1) to the operating pressure abnd then introduced into the ethylene separation step 4.