The Heating Surface Layout And Thermal Analysis Of The Double-reheat Ultra-supercritical Boiler

Under the condition of the existing heat-resistant steel system, the design andmanufacture of the double-reheat units with steam temperature600℃degree is the maindevelopment direction for ultra-supercritical technology in recent years, which is also aimportant approach to improve the heat rate of power plant uints.The design of double-reheat ultra-supercritical boiler is facing many difficulties, forexample, the matching between superheated steam heat absorption and reheated steamheat absorption, the measures for double reheated steam temperature regulation and thechoice of the water supply.This text has put forward the scheme for1350MW ultra-supercritical double-reheatcoal-fired boiler with Π-shaped and double flue gas passage in the end. The steamparameters of the boiler outlet is31.3MPa,605℃/623℃/623℃, and the thermalefficiency is94%(based on lower heating-value).In order to solve the difficulties of the double-reheat boiler design, the temperatureof water supply is320℃, which is as high as possible, to increase the extraction flow.The back pressure steam-driven feed pump has been used to decrease the reheated steamflow, and then decrease the reheated steam heat absorption, which is useful to reduce thedifficulties of the heating surface layout. In order to increase the heating transfer betweenthe furnace exit and the economizer exit, the gas temperature of furnace exit should beraised and the gas temperature of economizer exit should keep rational.Based on the standard method for boiler thermal calculation, the checked calculationhas been made for1350MW ultra-supercritical double-reheat, which include supportingcalculations, heating balance calculation, the checked calculation for furnace, thechecked calculation for superheater, the checked calculation for the reheater and doublereheater, the checked calculation for economizer and the heating balance calculation ofthe tri-section regenerative air preheater.The exhaust gas temperature, hot blast temperature and the heating balancecalculation are all been checked. All of the deviation are within the scope of the standard.