Integrated Beneficiation and Drying of Low Rank Coal in Air Dense Medium Fluidized Bed

摘要

High moisture and high ash of low rank coals (LRC) not only reduces its market value as a fuel and energy conversion efficiency, but also has its environmental footprint. Therefore, the possibility and advantages of integrating LRC drying and beneficiation processes at low temperatures (exhaust flue gas of a boiler) in an air dense medium fluidized bed (ADMFB) was investigated through comparison of packed bed and ADMFB coal moisture removal performances under varying operating conditions using the Boundary Dam lignite coal. The run of mine (ROM) ADMFB coal beneficiation was conducted and accordingly the clean coal product was introduced to the ADMFB dryer. The drying results showed that both superficial air velocity and hot air temperature are in favor of moisture removal regardless of which system was engaged even though, the ADMFB dryer exhibited better results than the packed bed dryer. Average moisture reduction of 71% was obtained for ADMFB drying of clean coal products. It is concluded that the organic phase releases freezable moisture a lot easier than high ash particles. The 39.8 to 59.8% moisture reduction achieved through co-ADMFB drying and cleaning with just 10 min process time which increases the HHV of ROM 15% from 21.78 MJ/kg to 25.16 MJ/kg. Also the drying kinetics study of packed bed and ADMFB drying results implemented better fitting of Page and Henderson & Pabis models for packed bed and ADMFB systems respectively. THE fluidization time is an important parameter. Time scale for two processes are very different..