The present invention relates to a heat exchange system for producing superheated working fluid for a steam turbine from expected supercritical hydrothermal fluid from a geothermal reservoir, comprising a header-type heater with a shell (10), where an inlet is conducted to a feed pipe (20) for transporting the expected supercritical hydrothermal fluid from the geothermal reservoir into the shell (10) and where an outlet is conducted to a drain pipe (30) for transporting the condensed hydrothermal fluid from the shell (10) to a disposal, working fluid pipes (70,80) circulating feed water from a condenser of the steam turbine into a heat exchange bundle system within the shell (10) and retrieving superheated steam from the heat exchange bundle system for the steam turbine, a spraying device (40) is arranged within the shell (10) for spraying a first (11) bundle of the heat exchange bundle system, and a mixing device (60) is arranged between an output of the first bundle (11) and an input of a working fluid down
