General Aspects of Coil and Soaker Reactors

The coil visbreaker is operated at high temperature and low residence time and, thus, is also termed as a high-temperature, short-residence-time (HTST) process. The feed enters the furnace at 300°C-330°C and undergoes thermal cracking in the coil at 460°C-480°C for 2-5 min. The cracking reactions occur in the liquid phase and are slightly endothermic (192kcal/kg of the 204 C-product). 

In coil-soaker operation, the feed is allowed to pass through the coil and is kept at relatively lower temperature ( 450°C) and residence time (2-3 min). After that, the product from the coil is passed to the soaker (adiabatic hollow drum) for a longer time (15-25 min). The reduction in the coil temperature and simultaneous increase in the residence time in the soaker give similar conversions as in the case of the coil type. Thus, the coil-soaker type is described as the low-temperature, high-residence-time (LTHT) process. The cracking reactions occur in both the coil and in the soaker. The temperature in the soaker reduces axially about 10°C-20°C due to the endothermic nature of the cracking reactions. 

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