Thermal cracking of a wide range of feedstocks into light olefins (mainly ethylene and propylene) and aromatics using proprietary cracking coils.
Feedstocks: Ethane, propane through liquid feeds up to heavy gasoil or up to 600°C EP.
Products: Cracked gas rich in Ethylene, propylene, butadiene and BTX (benzene, toluene and xylene).
Thermal cracking occurs in the presence of steam at high temperature in cracking coils located centrally in the firebox. Coil outlet temperature varies from 800°C up to 880°C depending on feed quality and cracking severity. The recent proprietary coils are GK6 and SMK coils used, respectively, for liquid and gas cracking. They feature high selectivity to ethylene, propylene, together with low coking rates (longer run length). Technip has also developed recently new patents (GK7 and Swirl Flow Tubes) to enhance both capacity and run length at lower investment cost.
Cracked gases from the furnaces coils pass through a transfer line exchanger (TLE) system, where heat is recovered to generate high-pressure steam. The primary TLEs are special S&T or linear types that ensure low to very low fouling rates and, thus, extending run lengths. Heat from the flue gases is recovered in the convection section to preheat feed and process steam, and to superheat the generated VHP. The technology is also applied to retrofit furnaces. The furnaces performances are optimized by using Technip’s proprietary software SPYRO. Depending on the regulations various, options of NOx abatement are incorporated.
Ethane conversion, % 65–75
Naphtha cracking severity 0.4–0.75
Overall thermal efficiency % 92–95
Coil residence time, sec
Once-through ethylene yields depend on feed characteristics and severity, and range from 58% for ethane to 36% for liquid feeds.