Abstract
Bio-based binders are suggested as a viable alternative to fossil-based coal tar pitch (CTP) binders in carbon anodes for aluminium production. In this study, upgrading of bio-condensates from pyrolysis of Norwegian spruce wood is done by slow heat treatment in small scale. Condensates were subjected to a heating rate of 0.5 °C/min with maximum temperature varying from 160 to 180 °C and holding time at maximum temperature varied from 1 to 3 hours. The produced materials were then subjected to a wetting test using an optical dilatometer, to observe the interaction between the binder and calcined petroleum coke during heating. The contact angle development between coke and binder varied between the different binder materials, ranging from good wetting for some samples to no wetting at all for other samples. Some results were more difficult to interpret; to confirm interaction between coke and binder in these cases, μCT imaging and light microscopy were applied to the samples after the wetting test. The imaging methods confirms the major differences between wetting and non-wetting behaviour observed in the original test, and also reveals that some of the bio-materials have relatively good interaction between coke and binder even without perfect wetting appearance during the wetting test. The imaging techniques are shown to be suitable methods to observe the interactions between coke and binders with different wetting ability. Many of the bio-binders produced seem to have a good wetting ability towards calcined petroleum coke, and are thus viable as an alternative to fossil-based binders in anodes.
