This dataset models a feedstock mix of naphtha, propane, and liquefied petroleum gas. At 800-900°C in a cracking furnace, longer-chain saturated hydrocarbons are broken down into shorter unsaturated compounds. The main products include ethylene and propylene, with hydrogen, mixed C4 hydrocarbons, and other co-products. Cracking-unit designs are broadly similar and require only minor modifications for local conditions. Naphtha remains the principal feedstock, although the shares of light components such as propane and butane and liquid feedstocks such as liquefied petroleum gas have increased in recent years. A portion of the by-product fuel gas is used in the cracking furnaces.
1. Cracking: Feedstocks entering the plant are preheated, mixed with dilution steam, and heated before cracking in the radiant section of the furnace. Liquid-feed furnaces use highly selective radiant coils for high-severity cracking, while gas-feed furnaces use multi-pass coils. Cracked gas is sent to the downstream separation section. Both liquid- and gas-feed furnaces are bottom-fired.
2. Separation: Heat is recovered from the cracked gas in a waste-heat boiler, after which the gas serves as stripping medium in the gasoline fractionator. The fractionator bottoms leave the plant as crude fuel oil, while the overhead stream is quenched in a quench-water tower and sent to compression. The demethanizer bottoms are sent to the deethanizer, and the deethanizer overhead enters an acetylene converter, where acetylene is selectively hydrogenated to ethylene and ethane.