Auxiliary boiler systems from natural gas which include stack, burner, boiler and sky in power plant. Drum for generator steam of HRSG boilers systems (Heat recovery steam generator) during construction in Combined-Cycle Co-Generation Power Plant. Drum for generator steam of HRSG boilers systems (Heat recovery steam generator) during construction in Combined-Cycle Co-Generation Power Plant. Drum for generator steam of HRSG boilers systems (Heat recovery steam generator) during construction in Combined-Cycle Co-Generation Power Plant.