TRANSFER-LINE HEAT-EXCHANGER FOULING DURING PYROLYSIS OF HYDROCARBONS.1. DEPOSITS FROM DRY CRACKED GASES

Isobutane of technical quality was pyrolyzed in nitrogen as a diluent under standardized conditions (820-degrees-C, 0.4 s, N2/isobutane = 0. 4 g/g) in a specially developed, vertically positioned tubular flow re actor coupled with a micro electrobalance. After cooling the dry crack ed gases to temperatures thought to be representative for the innertub e surface temperatures of a TLE (transfer-line exchanger), the growth of carbon-rich deposits (known as TLE fouling) was measured continuous ly at the surfaces of material coupons in dependence on (i) the prehis tory and (ii) the sort of materials as well as (iii) the temperatures. The results show clearly that on low alloyed steels catalytic reactio ns can play an important role in TLE fouling if dry cracked gases are used.