Pyrolysis characteristics of oil-field sludge and the comparison of kinetic analysis with two representative methods

Abstract

Abstract The pyrolysis of oil-field sludge (OS) has the appeal of resource recovery for this kind of waste disposal. In this paper, we investigate the pyrolysis kinetics of OS with Coast-Redfern (CR) and Flynn-Wall-Ozawa (FWO) methods in a wide temperature range (305–1223\u202fK). The pyrolysis process of OS mainly includes light organics vaporization (Stage-2), middle and heavy organics and carbonates decomposition (Stage-3), coke reduction and other inorganics decomposition (Stage-4). The kinetic analysis manifests that Stage-2 meets well with the reaction order mechanism, and the reaction order (n) is 2 and in the range of 1.3–1.9 obtained by CR and FWO, respectively. The divergence of the two methods mainly appears in Stage-3, where Ea calculated by FWO method is much higher than that by CR method. CR method gives D1 model for this stage, while FWO method picks D3 model to describe this stage. The simulation plots indicate that the results of CR method are more credible. As for Stage-4, both methods select G(α)\u202f=\u202fα as the mechanism, but CR method performs better agreement and a smaller discrepancy than FWO method does. Thus, FWO method is considered less accurate for OS analysis.