Device made of fabric for limiting or preventing the migration of particles between two layers

A device configured to be interposed between a lower layer and an upper layer of particles arranged inside a cylindrical shell, so as to limit or prevent the migration of particles between the layers, the device comprising a ring of fabric comprising:

• meshes of equivalent diameter smaller than the equivalent diameter of the particles,
• a length equal to the internal perimeter of the base of the cylindrical shell,
• an upper part having an upper end configured to be attached along its entire length to the internal wall of the cylindrical shell, and
• a lower part comprising at least six identical knife pleats, each pleat being formed by two creased edges that meet at a point, and the pleats being separated from one another in such a way that the lower part is substantially perpendicular to the upper part when the knife pleats are in the folded position.