Pyrolysis behaviors of oilfield sludge based on Py-GC/MS and DAEM kinetics analysis

Abstract

In this work, the effect of heating rate (10, 20, 50 and 100 K min−1) on oilfield sludge pyrolysis was studied on thermogravimetric analyzer (TG) and the pyrolysis kinetics was investigated by means of the distributed activation energy model (DAEM). The TG/DTG curves of oilfield sludge pyrolysis are shifted to higher temperatures evidently as the heating rates increase and the intensity of DTG peak is increased with the increase of heating rate. The pyrolysis process of oilfield sludge could be divided into two stage. Kinetics analysis by DAEM revealed that the activation energy (E) decreased from 99.54 to 44.19 kJ mol−1 in the conversion ratio range of 0.1–0.2, and then E raised up to 184.63 kJ mol−1 with increase of the conversion ratio. In addition, Py-GC/MS experiments were performed to investigated the types of products and their proportions in pyrolysis process of oilfield sludge at different pyrolysis temperature (758, 943 and 1193 K) and the corresponding mechanism for oilfield sludge pyrolysis was briefly discussed. Cracking depth of oilfield sludge can be significantly improved by increasing pyrolysis temperature, and the light molecule weight of hydrocarbons (C4C10) increased with the increase of pyrolysis temperatures. Moreover, the increase of pyrolysis temperature was also conducive to the decrease of the polycyclic compounds. However, there is an abrupt increase of aromatics yields (14.69%) when temperature is up to 1193 K. The change of content of gasoline and diesel range hydrocarbons in pyrolysis products of oilfield sludge with pyrolysis temperature was also discussed.