Visbreaking studies in the presence of soaker internals

Abstract

Coil-soaker visbreaking is a well-proven technology in terms of lower capital investment, lower operating cost, and low susceptibility to operational upsets. A significant improvement in the performance of this technology can be achieved by incorporating suitable internals in the soaker. In the present work, visbreaking studies using vacuum residues obtained from Indian refineries were performed in a pilot plant equipped with soaker. The soaker was retrofitted with a set of in-house-developed internals. Two different configurations of internals along with a benchmark case of soaker without internals were studied for three vacuum residue feeds. The coil outlet temperature was varied in the range of 410-440°C, while the soaker outlet pressure was maintained constant at ~1.2 MPa. The resulting visbroken products, namely, gas (G, C1-C4), gasoline (60-150°C), light gas oil (LGO, 150-350°C), vacuum gas oil (VGO, 350-500°C), and vacuum residue (VR, lumped product consisting of compounds with normal boiling point above 500°C [500°C⁺]) were quantified and characterized in detail. The effect of internals has been studied on the conversion and the selectivity of the visbreaking reactions. The work brings out the advantages of internals in the visbreaking technology.