Method of production of ethylene at the basis of liquefied natural gas containing methane and heavier hydrocarbons with regasifying the liquefied natural gas

摘要

Vaporized methane, and ethylene are obtained from liquefied natural gas containing methane and heavier hydrocarbons by fractionating in a first demethanizer to obtain vaporous methane overhead and a heavier hydrocarbon bottoms, cracking the latter to produce a gas mixture containing methane and ethylene, separating the methane in a second demethanizer and passing the liquefied natural gas before fractionation through a heat exchanger to condense reflux for the second demethanizer and subsequently through a heat exchanger to condense reflux for the first demethanizer. Liquefied natural gas from store 10 is pumped by line 11 through heat exchangers 12, 13, 14, 15, 16 and 17 to first demethanizer 20. Vapour may be separated intermediately, e.g. in separator 18. Methane is obtained overhead and partially condensed in heat exchanger 16, vapour being removed by line 29 and liquid being refluxed by line 28. Bottoms may be split into ethane C2 hydrocarbons (line 32), C3 (line 33) and C4 (line 34) by fractionators 21 and 22 for separate cracking in cracking plant 35 or may be cracked without separation. After cooling and drying the combined products are split into two streams in lines 40 and 41 for cooling with methane vapours and liquid respectively before being fed into second demethanizer 23. Overhead is partially condensed in heat exchanger 12 to provide reflux. The bottoms are further separated into ethylene (line 59), ethane/bottoms from fractionator 25) and C3 and higher hydrocarbons (bottoms from fractionator 24). PICT:1011518/C4-C5/1