A grate arrangement for a furnace, the grate arrangement comprising
- a fixed step frame with supporting members;
- a movable step frame with supporting members, the movable step frame configured to drive in a reciprocating motion in a longitudinal direction;
- a first arrangement comprising a non-driven horizontal row of fixed grate bars and comprising movable grate bars,
- the fixed grate bars being fixed with respect to a supporting member of the fixed step frame and the movable grate bars being movable in the longitudinal direction with respect to a supporting member of the fixed step frame;
- and
- a second arrangement comprising a driven horizontal row of fixed grate bars and comprising movable grate bars, the fixed grate bars being fixed with respect to a supporting member of the movable step frame and the movable grate bars being movable in the longitudinal direction with respect to a supporting member of the movable step frame, the second arrangement of fixed grate bars and movable grate bars vertically overlapping the first arrangement of fixed grate bars and movable grate bars
- wherein each of the fixed grate bars and the movable grate bars of the first arrangement and the second arrangement comprise
- a first lateral side, a second lateral side, and an upper surface, the second lateral side being opposite to the first lateral side and the second lateral side facing into a direction that is opposite to a direction in which the first lateral side is facing,
- the upper surface of each grate bar being provided between the first lateral side and the second lateral side of the grate bar, wherein the first lateral side and the second lateral side are integrally formed with the upper surface and are separated by the upper surface,
- each grate bar further comprising a first elongated recess and a second elongated recess defined at the first lateral side, each of the elongated recesses having two parallel sliding surfaces and defining a height as a distance between the two parallel sliding surfaces,
- each grate bar further comprising a first engaging element and a second engaging element, the first engaging element and the second engaging element disposed on the second lateral side, each of the engaging elements defining two parallel sliding surfaces and defining a height as a distance between the two parallel sliding surfaces,
- wherein a longitudinal dimension of the first elongated recess is greater than a longitudinal dimension of the first engaging element, and a longitudinal dimension of the second elongated recess is greater than a longitudinal dimension of the second engaging element,
- the engaging elements of each grate bar being provided for engaging into corresponding elongated recesses of a first neighboring grate bar and the elongated recesses of the grate bar being provided for taking up corresponding engaging elements of a second neighboring grate bar,
- each grate bar further comprising a downwardly extending portion and a protrusion downwardly disposed on the grate bar, the downwardly extending portion and a vertical part of the protrusion defining a space.