The process of division - combining of streams in mixers with bars and radial and longitudinal scrapers was studied. The number of unique streams that are formed after passing each row of longitudinal bars and the total amount of them were determined. This is demonstrated by migration of the particles along the mixer from left to right and vice versa, from the center of the drum towards the periphery and vice versa. In the process of mixing the particles in the center gain normal distribution and the ones on the side - sectioned normal distribution. The sum of normal distribution with the sectioned normal distribution leads to an equable distribution along the drum and transverse planes and to a homogeneous mixing of the components. The quality of mixing had been investigated and an optimal mixing regime for the mixer with radial and longitudinal bars and scrapers was proposed.