Abstract: A steam generator having a coal fired furnace including water cooled walls, and having a hopper bottom. A plurality of steel struts are provided which extend between the furnace walls at a level at or above the top of the hopper bottom, and the furnace inlet ring header located at the bottom of the hopper, so that the unit can be bottom supported. The steam generating tubes extending upwardly out of the ring header and forming the furnace walls each contain a bend therein, so as to be flexible enough to accommodate differential thermal growth of the struts relative to the adjacent furnace walls during transient temperature occurrences.