Improvement on slurry ability and combustion dynamics of low quality coals with ultra-high ash content

It is a significant subject that low quality coals could be used for high concentration slurry preparation because of the large reserve and low price. Nevertheless, due to the microstructure and surface properties of low quality coals, it is difficult to prepare qualified coal water slurry (CWS) directly. In this study, an improved flotation technique was employed to upgrade two low quality coals, then Jinda raw coal (JD-RC) and its upgraded coal (JD-UC), together with Jisuo raw coal (JS-RC) and its upgraded coal (JS-UC) were applied to CWS preparation and combustion dynamics analysis. Results showed that after two samples of low quality coals were upgraded, the maximum slurry concentration could be increased by 6%. It was attributed to the variation of free water content, which was mainly influenced by composition and pore structure of coal particles. Because of the remarkable decrement on specific surface area and porosity after flotation, the ignition temperature and apparent activation energy of CWS prepared by JD-UC were increased comparing to JD-RC. However, the ignition temperature and apparent activation energy of CWS prepared by JS-UC were lower than JS-RC, which was resulted from the higher combustible content in JS-UC. The results of this study provided a method for the preparation of high concentration CWS using low quality coals with ultra-high ash content.