A device for fluidizing at least one substance which in a fragmented state is received in a confined space of the device, and the space having at least one outlet enabling the fragmented, fluidized substance(s) to leave said space at a lower region thereof as an end product, comprising: at least one set (205; 206) of rotary shovels located in said space, the at least one set of rotary shovels being located on a common rotary shaft (211; 212) of the set, the shaft being configured to rotate in a first rotating mode when operating to fluidize the fragmented substance(s), and the shovels (213 - 217; 218 - 222) of at least one set of shovels extending radially from a respective surface of the common rotary shaft (211; 212), each shovel, as viewed radially from the rotary shaft, having a curved cross-section so as to present upon rotation of the set of shovels a convex surface (213' - 217'; 218' - 222') to face the fragmented substance(s) to be fluidized, and each shovel at a radially outer region (213" - 217"; 218" - 222") being forwardly flared in a direction of a fluidizing mode of rotation, i.e. in a direction of the convex side of the shovel surface, the outer region thereby having a forward face forming an angle with the rotary forwardly facing convex surface of the remainder of the shovel, characterized in that a concave side of the shovel is covered by a member (227, 227',227"; 228, 228', 228"; 229; 230) to yield that a space between said concave side and the member yields a sealed cavity, and that the member is: either a) a plate member (227, 227', 227"; 228, 228', 228") extending between side edges of the shovel, or b) an aerodynamic member (229; 230) having a drop shaped or wedge shaped configuration which extends rearwards from the concave side of the shovel, transversely of a radial direction of the shovel, and has its widest dimension closest to said concave side. at least one set (205; 206) of rotary shovels located in said space, the at least one set of rotary shovels being located on a common rotary shaft (211; 212) of the set, the shaft being configured to rotate in a first rotating mode when operating to fluidize the fragmented substance(s), and the shovels (213 - 217; 218 - 222) of at least one set of shovels extending radially from a respective surface of the common rotary shaft (211; 212), each shovel, as viewed radially from the rotary shaft, having a curved cross-section so as to present upon rotation of the set of shovels a convex surface (213' - 217'; 218' - 222') to face the fragmented substance(s) to be fluidized, and each shovel at a radially outer region (213" - 217"; 218" - 222") being forwardly flared in a direction of a fluidizing mode of rotation, i.e. in a direction of the convex side of the shovel surface, the outer region thereby having a forward face forming an angle with the rotary forwardly facing convex surface of the remainder of the shovel, characterized in that a concave side of the shovel is covered by a member (227, 227',227"; 228, 228', 228"; 229; 230) to yield that a space between said concave side and the member yields a sealed cavity, and that the member is: either a) a plate member (227, 227', 227"; 228, 228', 228") extending between side edges of the shovel, or b) an aerodynamic member (229; 230) having a drop shaped or wedge shaped configuration which extends rearwards from the concave side of the shovel, transversely of a radial direction of the shovel, and has its widest dimension closest to said concave side. either a) a plate member (227, 227', 227"; 228, 228', 228") extending between side edges of the shovel, or b) an aerodynamic member (229; 230) having a drop shaped or wedge shaped configuration which extends rearwards from the concave side of the shovel, transversely of a radial direction of the shovel, and has its widest dimension closest to said concave side.