Energy saving by pre-drying moist fuels and recovery of the exhausted vapour enthalpy

Pre-drying of tre humid coal is the only solution environmentally and economically concerned. There are different possible processes as thermal drying, thermal dehydration, thermo-mechanical drying, by means of different heat and mass exchange systems (fluidized bed, tubular heat exchangers, classical heat exchangers which could be of contact or convective type). All varieties must fulfil several conditions, such as high mass coal flow, efficient vaporization, safety and low additional energy consumption. The following ones must be respected: minimal pressure looses of gas phase; enhanced contact surface and residence time between the two phase; reasonable reduction of energy consumption and simple design and compact construction. A lab-scale facility for pre-drying of lignite coal in fluidized bed and simultaneous vapour enthalpy recovery is proposed as the best solution for enhancing the general efficiency of the unit and reducing CO2 emission