Modeling Coil and Soaker Reactors

Coil and soaker reactors can be classified as gas-liquid systems wherein the dispersed phase is composed by the produced gas, the vaporized low molecular weight hydrocarbons, and superheated steam, while the continuous phase comprises the visbroken residue. Based on this, the coil reactor can be represented as a two-phase plug-flow reactor (PER) or as a series of equal-volume continuous-stirred tank reactor (CSTR), while the soaker reactor can be modeled as a bubble-column reactor or as CSTR. Visbreaking reactions proceed via free radical mechanism and take place in the liquid phase, being the feed flowrate that decides the liquid-phase residence time in both reactors. 

The operating pressure has an indirect effect on the liquid-phase residence time. Increasing its value suppresses the vaporization of low-boiling fractions, thus increasing the liquid-phase holdup and the liquid-phase residence time. In addition. 

Modeling visbreaking reactors has been proposed by several groups to be performed by using various approaches, as in the following (Joshi et al., 2008)  

As can be observed, both coil and soaker reactors have been modeled in the literature by following different approaches, and their validation has been performed with experimental data (batch reactor and pilot-plant data) and connnercial data either for coil visbreaking or for coil-soaker visbreaker. 

The coil reactor can be modeled with the PFR equation of design  

---