We study two-phase flow in a tall vertical slot differently heated from the side walls, where one of the phase is fluid and another phase consists of small solid particles. The particles are subjected to downward drag exerted by the gravity and the drag exerted by finite-frequency horizontal vibrations along the layer. In the framework of the generalized Boussinesq approximations we derive non-contradictive set of governing equations describing the dynamics of suspension. The pulsed base flow is obtained and its linear stability is analysed. The comparison of the numerical results with the recent experimental findings is given.