Study on integration of drying and separation for lignite by hot airflow gas–solid fluidized bed

[Display omitted] •Hot airflow and impeller are introduced into the gas–solid fluidized bed.•Effect of impeller on fluidization and drying performance of fluidized bed is studied.•Operational parameters are optimized for dry beneficiation of lignite.•Integration of drying and separation of high-moisture lignite is achieved. With the continuous consumption of high-quality coal, the efficient development of lignite resources is an important guarantee for the stable and sustainable development of coal industry. Due to the characteristics of lignite with high moisture content, its efficient separation is still a great challenge faced by the current industry. In this study, to improve the dry beneficiation efficiency of lignite, hot airflow and impeller were introduced into the gas–solid fluidized bed to achieve the integration of drying and separation for lignite. Effects of the impeller diameter, airflow velocity, airflow temperature and impeller speed on the drying features and the fluidization characteristics of hot airflow gas–solid fluidized bed were investigated. Drying and fluidization tests indicated that the appropriate operational factors of impeller diameter of 61 mm, airflow velocity of 1.2Umf (that is, Umf is the minimum fluidizing airflow velocity), airflow temperature of 110 °C and impeller speed of 60 r/min should be adjusted to obtain the optimum fluidization environment for the drying and separation of lignite. Under the optimal operating conditions, a high-quality clean coal with ash content of 9.72 %, moisture content of 13.13 %, and calorific value of 4318.33 cal/g was obtained for 25–13 mm lignite, while that with ash content of 13.41 %, moisture content of 12.70 %, and calorific value of 4120.22 cal/g was obtained for 13–6 mm lignite. Efficient drying and separation of lignite could be realized by using the hot airflow gas–solid fluidized bed. This study provides theoretical guidance for efficient beneficiation of lignite resources with high moisture content by hot airflow gas–solid fluidized bed.