Role of water and fine solids in onset of coke formation during bitumen cracking

The aim of this study was to examine the effect of water and fine solids on coke formation during thermal cracking of a residue fraction from vacuum distillation (Athabasca vacuum tower bottoms) and Athabasca bitumen froth. Experiments were conducted in a batch reactor with 0-33.3 wt.% water at 410 °C for up to 80 min to measure the time of onset of coke formation, total coke yield as a function of time, and conversion of vacuum residue. Removal of fine solids significantly shortened the onset time of coke formation, but the addition of water had no significant impact on onset time. The yield of cracked products, as determined by simulated distillation, was insensitive to the presence of water and fine solids. Based on the findings from this study, it was concluded that residual fine solids have a beneficial effect on thermal upgrading as they delayed the onset of coke formation, while water has little impact within the tested concentration range of 0-33 wt.% water.