Alumina particles with an initial moisture content of 5 kg per kg dry solid are dried in a batch dryer. For the first two hours, the measured drying rate is constant at 2 kg m\(^{-2}\) h\(^{-1}\). Thereafter, in the falling-rate period, the rate decreases linearly with the moisture content. The equilibrium moisture content is 0.05 kg per kg dry solid, and the drying area of the particles is 0.5 m\(^2\) per kg dry solid. The total drying time, in hours, to reduce the moisture content to half its initial value is: