Grate block for a combustion grate

A grate block for a combustion grate, wherein the grate block comprises a block body that has an upper wall and defines a longitudinal axis, wherein the upper wall forms a bearing face along which the incinerator charge is to be conveyed and the foremost end of which, when viewed in a thrust direction, aligned substantially parallel to the longitudinal axis, forms an edge by way of which the bearing face descends into a thrust surface formed by a front wall, the front wall has a lower bearing edge which is disposed in a plane running substantially orthogonally to the longitudinal axis and specified for coming into contact with the bearing face of a grate block adjacent in the thrust direction, wherein the upper wall has an air supply opening formed by an air supply duct running through the upper wall, wherein

• the air supply opening is at least partially surrounded by a thickening which projects from the bearing face and forms a protection duct, which extends the length of the air supply duct, and is specified to prevent liquid flowing into the air supply opening, wherein the protection duct is enclosed by an inner flank of the thickening and the thickening has an outer flank that adjoins the inner flank and runs in a descending manner on the side that faces away from the protection duct.