FIELD: heat-power engineering; generation of steam. SUBSTANCE: once-through steam generator is provided with two flue ducts interconnected through horizontal flue duct; according to invention, many parallel tubes for fluid medium are interconnected forming evaporating heating surface which is part of external wall of first flue duct; steam generator tubes forming evaporating heating surface enter common header on outlet side which is located lower as compared with lower edge of horizontal flue duct; said header is connected with platen heating surface located in area of first flue duct above combustion chamber; platen heating surface is connected with steam-and-water mixture separator. In starting the steam generator, flow rate of water in tubes is reduced as soon as water starts escaping from tubes forming evaporating heating surface enter common header on outlet side which is located lower as compared with lower edge of horizontal flue duct; said header is connected with platen heating surface located in area of first flue duct above combustion chamber; platen heating surface is connected with steam-and-water mixture separator. In starting the steam generator, flow rate of water in tubes is reduced as soon as water starts escaping from tubes forming evaporating heating surface. EFFECT: enhanced reliability due to reduction of thermal stresses. 4 cl, 3 dwg
