Method for coating bulk material comprising: - starting a coating apparatus (1; 101) according to a start procedure on a discrete load of bulk material to be coated; - operating said coating apparatus (1; 101) in stationary mode by introducing a continuous flow of uncoated bulk material into said coating apparatus (1; 101) and obtaining at the outlet of said coating apparatus (1; 101) a continuous flow of coated bulk material having a predetermined stationary coating weight gain (W%); wherein said coating apparatus (1; 101) comprises: - a first rotatable tubular container (2; 102) arranged to receive and discharge bulk material, said first rotatable tubular container (2; 102) being provided with a first dispensing device (5; 105) for dispensing coating material on the bulk material in a plurality of internal successive adjacent spray zones between a first inlet and a first outlet of said first rotatable tubular container (2; 102); - a second rotatable tubular container (6; 106) arranged to receive bulk material coming from said first rotatable tubular container (2; 102), said second rotatable tubular container (6; 106) being provided with a second dispensing device (9; 109) for dispensing coating material on the bulk material in a plurality of internal successive adjacent spray zones between a second inlet and a second outlet of said second rotatable tubular container (6, 106); - conveying means arranged to convey the bulk material from said first rotatable tubular container (2; 102) to said second rotatable tubular container (6, 106); characterized in that said method further includes in succession the steps of: - dispensing coating material on said load while maintaining said load internally of said first rotatable tubular container (2; 102) until coated bulk material having said predetermined stationary coating weight gain (W%) is obtained; - a transition phase to said stationary mode in which there is provided transferring a flow rate of said load of coated bulk material from said first rotatable tubular container (2; 102) to said second rotatable tubular container (6; 106) and feeding said first rotatable tubular container (2; 102) with a same flow rate of bulk material to be coated; - dispensing coating material on said same flow rate of bulk material to be coated entering said first rotatable tubular container (2; 102) by sequentially activating the spray zones inside said first rotatable tubular container (2; 102) to obtain at said first outlet a bulk material partially coated with a preset weight gain (U%); - dispensing coating material on said same flow rate of bulk material partially coated with said preset weight gain (U%) entering said second rotatable tubular container (6; 106) by sequentially activating the spray zones inside said second rotatable tubular container (6, 106) to obtain a bulk material coated with said predetermined stationary coating weight gain (W%). - starting a coating apparatus (1; 101) according to a start procedure on a discrete load of bulk material to be coated; - operating said coating apparatus (1; 101) in stationary mode by introducing a continuous flow of uncoated bulk material into said coating apparatus (1; 101) and obtaining at the outlet of said coating apparatus (1; 101) a continuous flow of coated bulk material having a predetermined stationary coating weight gain (W%); - a first rotatable tubular container (2; 102) arranged to receive and discharge bulk material, said first rotatable tubular container (2; 102) being provided with a first dispensing device (5; 105) for dispensing coating material on the bulk material in a plurality of internal successive adjacent spray zones between a first inlet and a first outlet of said first rotatable tubular container (2; 102); - a second rotatable tubular container (6; 106) arranged to receive bulk material coming from said first rotatable tubular container (2; 102), said second rotatable tubular container (6; 106) being provided with a second dispensing device (9; 109) for dispensing coating material on the bulk material in a plurality of internal successive adjacent spray zones between a second inlet and a second outlet of said second rotatable tubular container (6, 106); - conveying means arranged to convey the bulk material from said first rotatable tubular container (2; 102) to said second rotatable tubular container (6, 106); - dispensing coating material on said load while maintaining said load internally of said first rotatable tubular container (2; 102) until coated bulk material having said predetermined stationary coating weight gain (W%) is obtained; - a transition phase to said stationary mode in which there is provided transferring a flow rate of said load of coated bulk material from said first rotatable tubular container (2; 102) to said second rotatable tubular container (6; 106) and feeding said first rotatable tubular container (2; 102) with a same flow rate of bulk material to be coated; - dispensing coating material on said same flow rate of bulk material to be coated entering said first rotatable tubular container (2; 102) by sequentially activating the spray zones inside said first rotatable tubular container (2; 102) to obtain at said first outlet a bulk material partially coated with a preset weight gain (U%); - dispensing coating material on said same flow rate of bulk material partially coated with said preset weight gain (U%) entering said second rotatable tubular container (6; 106) by sequentially activating the spray zones inside said second rotatable tubular container (6, 106) to obtain a bulk material coated with said predetermined stationary coating weight gain (W%).