ABSTRACT
Ethylene is the largest volume hydrocarbon used in the petrochemical industry. Ethylene is produced by steam cracking from a wide range of hydrocarbons including ethane, propane, butane, naphtha, liquid petroleum gas and gas oils. Ethylene plants based on ethane are cheaper to construct, less complicated to operate, give high yields with minimal by-products and are attractive to companies not fully integrated to market propylene and aromatics associated with naphtha cracking. The hydrocarbon stream is heated and then diluted by mixing with steam before entering a tubular reactor. Depending on the feedstock used, cracking takes place at a temperature of 750–870°C under partial pressure with a residence time of up to one second. Any unconverted propane is recycled to the reactor. Bottoms from the fractionator pass into a butene purifier where high-purity butenes are collected overhead. Propylene conversion per pass is around 40%.
