(617d) Modeling of Circulating Fluidized Bed Reactors for the Selective Oxidation of Alkanes By Chemical Looping

Authors: 
Neal, L., North Carolina State University
Haribal, V. P., North Carolina State University
Li, F., North Carolina State University
The thermal cracking of alkanes is a major source for olefin production worldwide. The North American shale oil and gas boom has greatly increased the supply of light alkanes, reduced the cost of feedstock for olefin production, and spurred the expansion of worldwide cracking capacity. Unfortunately, conventional cracking processes, which rely upon significant steam dilution and high temperature furnaces, are leading drivers of CO2 emissions in the chemical industry. We have recently introduced chemical looping systems for Redox Oxidative Cracking (ROC) of natural gas liquids, condensates, and light naphtha. In ROC, a metal oxide’s (or oxygen carrier’s) lattice oxygen is used to partial oxidize the alkane, producing water. Subsequent regeneration of the oxygen carrier’s lattice oxygen in air produces significant process heat. ROC effectively provides heat to endothermic cracking reactions by selectively burning hydrogen byproducts via chemical looping combustion. In this work, we present modeling methods for ROC in circulating fluidized bed reactors for evaluation of this emerging technology. The model incorporates experimental measurements of a hexane ROC redox catalyst. We show that lost work in the reactor sections can be reduced compared to both conventional cracker furnaces and oxygen co-feed systems. A significant reduction in lost work is still observed when the effects of different fuels (e.g. H2 vs. natural gas) are incorporated.