The three-dimensional intrinsic convection in a monodisperse dispersion of spheres settling in a vertical container of arbitrary cross section is calculated using the simple model of point forces with excluded volume near the walls, proposed by Bruneau et al. [Phys. Fluids 8, 2236 (1996)]. An exact solution of the model equations for a container with rectangular cross-section shows that corners have no significant influence on the convection. A dense suspension is modeled by assuming an equilibrium particle distribution in the near wall region. It is predicted that as a result of near wall ordering, the intrinsic convection decreases with increasing particle volume fraction.