In view of the common problems occur in utility boilers

such as low reheat steam temperature and failure operation of SCR flue gas denitration system at low load

a technical program of utility boiler coupling straw adiabatic direct combustion furnace was proposed. In this program

the flue gas temperature of boiler tail flue is directly increased by using the sensible heat of high temperature flue gas produced by straw combustion.Taking an ultra supercritical 350 MW unit boiler as the example

thermodynamic calculation and economic analysis were performed when the high temperature flue gas produced by straw combustion in adiabatic direct firing boiler was introduced to the inlet flue duct of the low temperature reheater and the flue duct in front of the SCR denitration system at different loads. The results show that

when the 1 000 ℃ high temperature flue gas was sent to the inlet flue duct of low temperature reheater at 100% load

the consumption of straw was 3 749 kg/h

the reheat steam temperature increased by 13.5℃ and the power supply coal consumption reduced by 1.86 g/(kW·h).At 50% load

the consumption of straw was 3 749 kg/h

the reheat steam temperature increased by 33.3℃ and the power supply coal consumption reduced by 7.39 g/(k W·h). When the 1 000 ℃ high temperature flue gas was sent to the flue duct in front of the SCR flue gas denitration system at 50% load

the consumption of straw was580 kg/h

the flue gas temperature at the SCR denitration system inlet increased by 8.7℃ and the power supply coal consumption increased by 0.84 g/(kW·h)

which met the requirements of the SCR denitration system.