SZS series boiler is double drums, longitudinal arranged, “D” type chamber structure. Furnace is on right side and convection tube bundle is on the left. The body is fixed on the basement by middle and both end flexible supports and make the boiler to expand horizontally to sideways. Around furnace is membrane water cooling tube wall. Furnace and tube bundle is totally separated by the membrane water wall at the left side of the furnace. The back part of bundle is sparse shift structure, front part is aligned structure. Smoke from furnace outlet enters re-burning chamber, bundle area, and then from left front part enters spiral fin coil economizer and condenser, finally discharged to atmosphere through chimney.