The paper presents an analysis of the effect of collisions between coarse and fine particles in the vertical flow of a streamof fine particles suspended in gas on the exchange of momentum in these conditions. It was found that the phenomenon of double collisions of fine particles with the surface of coarse particles can be observed during the flow of a stream of fine particles suspended in gas around moving and stationary coarse particles. This phenomenon changes the nature of the relationship between the force of mutual interactions and mass flow rate of fine particles. The proposed corrective relationship significantly improved the consistency of the value of coarse particle terminal velocity depending on mass flow rate of fine particles suspended in the gas flowing around coarse particles. The range of importance of the relationships concerning the terminal velocity of coarse particles was determined. (c) 2020 Published by Elsevier B.V.