Boiler system with a support construction

A boiler system comprising:

• a support construction;
• and
• a furnace supported to the support construction at a vertically middle section of the furnace, the furnace being enclosed by water tube walls comprising two side walls and two end walls, a roof, and a bottom, the side walls having a total height H from the bottom to the roof, wherein each of the two side walls comprises a vertical upper portion that extends from the roof to a level of thirty to seventy percent of the height H, a lower portion that extends from the bottom to a level of thirty to seventy percent of the height H and has a vertical upper portion of the lower portion of the side wall, and an in downward direction, outwards bent intermediate portion, at a level between the vertical upper portion of the side wall and the vertical upper portion of the lower portion of the side wall,
• wherein (i) the support construction comprises horizontal wall supporting beams at a level below the roof of the furnace,
• (ii) the horizontal wall supporting beams are arranged parallel to the two side walls and directly above the vertical upper portions of the lower portions of the two side walls, and
• (iii) the furnace is supported to the support construction by having the intermediate portions of the two side walls connected to the horizontal wall supporting beams so as to balance vertical loads of the furnace.