Pyrolysis of asphaltenes in an atmospheric entrained flow reactor: A study on gasification reactivity and properties of chars

Abstract

Solvent deasphalting, followed by asphaltenes gasification, has been recommended as a favorable alternative to coker based upgrading processes. However, very limited work has been carried out on pyrolysis and gasification of asphaltenes, at entrained flow conditions. The present work aims at addressing this gap. Chars were prepared in an atmospheric entrained flow reactor, at different process conditions. Several characterization techniques viz. SEM, EDX, XRD, FTIR, ICP-MS, TGA etc. were used to identify the changes in morphology, structure and properties of chars. Individual char particles were observed as having hollow structures, with porous walls. Effect of pyrolysis temperature, was observed to be much more prominent, than the effect of residence time (between 5-12s). Global gasification reactivity of different chars, was compared at a fixed temperature and concentration of CO2 and steam. Chars obtained at higher temperatures exhibited lower H/C ratio, and had lower content of heteroatoms. Graphitization of chars was observed at higher temperatures. Consequently, chars obtained at higher operating temperatures, demonstrated lower gasification reactivity. Vanadium and nickel present in asphaltenes, accumulated in chars. Kinetic parameters for pyrolysis, and heterogeneous char steam/CO2 reactions were estimated. Gasification reactions were observed, to be 5-6 orders of magnitude, slower than pyrolysis reactions. Temperature, velocity profile and residence time for particles in the DTF were also estimated by mathematical models (COMSOL Multiphysics).