A process wherein primary air supplied to the combustion bed through the thrust combustion grate is deflected after exiting from a surface of the thrust combustion grate by deflector elements mounted on the surface of the thrust combustion grate. The grate required for this purpose has grate plates made from a permeable hollow element with connection pieces for supplying and draining cooling water, with primary air supply ducts that run through the grate plate from a bottom to a top. Deflector elements against which the primary air exiting the outlet is intended to impact, are disposed over openings of the primary air supply ducts.