Transfer line exchangers

Ethylene (C2H4) and some other byproducts like propylene are produced by thermal cracking of hydrocarbons in pyrolysis furnaces. This process generates so-called cracked gas. Ethane, naphtha and other mineral oil fractions are predominantly used as feedstocks.

The cracked gas, which leaves the furnace at a temperature of around 850 °C (1,500 °F), must be cooled down rapidly to 250 - 400 °C to prevent secondary reactions and to stabilize the gas composition in order to obtain the optimum product yield. This process is called „Quenching“. In all modern ethylene processes this rapid cooling of the cracked gas is performed with Transfer Line Exchangers (also known as quench coolers or TLEs), thereby producing also valuable high pressure steam that can be used e.g. for steam turbines.

There are one or more parallel TLEs per furnace cell, which are connected by riser and down comer piping with one common, elevated steam drum thereby forming the so called quench system.