Ethylene Production from Propane

The process under analysis comprises three major sections: (1) Cracking and Quenching; (2) Compression and Drying; and (3) Separation.

Cracking & Quenching. Propane is fed to furnaces in which it is cracked, forming Ethylene, propylene, and other by-products. The furnace outlet stream is routed to a quench, to prevent further reactions and formation of undesirable by-products. From a decanter downstream the quench tower, heavy hydrocarbons and water to waste treatment are removed. Cracked gas from the quench is sent to compression and separation.

Compression & Drying. The compression of the cracked gas is performed across 5 stages. After the third stage, carbon dioxide and sulfur are removed from cracked gas by caustic soda and water washes in a caustic scrubber. The compressed cracked gas is cooled and then dried in molecular sieves, so that most of the water is removed.

Separation. The dried cracked gas is fed to a cold box to remove hydrogen and light hydrocarbons, minimizing Ethylene losses. Condensates are fed to separation columns. In the demethanizer, methane is separated from the main stream that is fed to the deethanizer. The top of the deethanizer is fed to an acetylene converter and then fractionated in the C2-splitter. Ethylene is obtained as main product. The deethanizer bottom stream is fed to a depropanizer, which distillates C3 components. This stream is catalytically hydrotreated for impurities removal, and then fed to the C3-splitter. PG propylene is drawn from the column as a side stream. The Depropanizer bottom stream is separated into a crude C4 stream, recovered as column overhead product, and pyrolysis gasoline by-product. The crude C4 stream is condensed and fed to extraction columns, in order to separate raffinate-1. The crude butadiene stream is fed to the distillation columns so as to purify butadiene.