The paper presents an analysis of the most important parameters affecting the progress and effectiveness of separation of ground yellow lupine mixtures, variety Amulet. The theoretical relationships and correlations between various factors of the process were determined. The effectiveness of pneumatic separation process was evaluated by determining the coefficient of separation h. It was shown that an increase of moisture content of the mixture causes a significant decrease in the coefficient h. Increase of moisture content by 2% caused a decrease of the separation efficiency by an average of 8.1%. An increase of the air flow velocity increases the value of h, but also increases the amount of valuable fractions which escape with the air flow. It was found that with increasing air velocity of V₁ = 7.8 m s^-1 to V₂ = 10.5 m s^-1 (within the moisture content of W₁= 10.1%, and W₄= 15.7%), the highest increase in this parameter was 16.1-38.2%. Based on the obtained results, a mathematical model of the separation of mixtures of biological ground materials was developed and verified. It can be used in planning and carrying out pneumatic separation and calculating the parameters of the particles of individual components of granular mixtures in air ducts.