An employee was disconnecting a braided metal flex hose that was supplying air to a furnace for the de-coking process. A supplier sent an alternate feed to the furnace, which required the furnace to remain online. The employee went to disconnect the flex hose from the furnace and received second degree burns to the face and first degree burns to the torso from steam/hot condensate. The line was not depressurized at the time of the incident.