A grate bar has a grate bar head, two side walls, a running surface behind the head and between the side walls and an underside disposed below the surface and between the side walls. A recess in one side wall forms an air slot between the surface and underside and is arranged only on one side wall, not in its opposite side wall. In a grate bar arrangement including multiple grate bars, each including a running surface and a grate bar head, in which an upper grate bar with grate bar head is moveably arranged relative to a lower grate bar so that the head may slide over front and rear grate bar running surface areas, the running surface has air slots in the front and rear areas and the head is displaceable relative to these slots so that the opening cross section of all slots remains constant.

The present application discloses a grate bar for a thrust grate of a furnace. The grate bar comprises an elongated recess at a first side of the grate bar. The elongated recess comprises two parallel sliding surfaces which are oriented in longitudinal direction of the grate bar. An engaging element is provided at a second side of the grate bar, which is opposite to the first side. The engaging element comprises two parallel sliding surfaces which are oriented in longitudinal direction of the grate bar. The elongated recess is shaped such that a corresponding neighbouring engaging element of a neighbouring part is movable within the elongated recess in the longitudinal direction relative to the grate bar. The grate bar further comprises two actuating surfaces at a bottom side of the grate bar for taking up a protrusion of a grate.