Lummus Technology Heat Transfer (LHT) has developed seven generations of SRT®, Short Residence Time, pyrolysis furnaces. SRT-I was developed in the mid-1960s as a response to growing ethylene demand. The last four generations (SRT IV, V, VI and VII) feature a unique, two-pass radiant coil design that is mechanically simple and easy to operate.

LHT has built more ethylene cracking furnaces than any other process licensor, representing 40% of worldwide ethylene capacity. The SRT pyrolysis furnace consistently achieves designed capacity, meets yield guarantees, and operates for longer run lengths (greater than 50 days) between coil decokings.

In cooperation with Alstom, LHT developed the proprietary transferline exchangers "Bath Tub" and "Quick Quencher". Both provide higher yield and longer run length. Many SRT designs feature gas turbine integration with the furnace to significantly improve the plant energy balance. Recent projects are equipped with low NOx burners or catalytic De-NOX systems to improve emissions.