The double-tangential combustion boiler in an ultra supercritical 1 000 MW unit is studied by theoretical analysis and simulation calculation. The main factors that restricting the steam temperature improvement and causing the thermal deviation of the heated surface of the boiler are analyzed

and the methods for steam temperature improvement of different heating surfaces are proposed. The actual application results indicate that

after transformation using the steam temperature improvement scheme proposed by this paper

the main steam and reheat steam temperature of the unit increased by about 15 ℃ and 13 ℃

respectively

and the coal consumption reduced by about 2.5 g/(kW·h)

which achieved the expected effect. The safety and economic operation of the unit has been obtained.