Study On The Selection Of Boiler Type For2×660MW Ultra-supercritical Units In Jiujiang Power Plant

Supercritial&ultra-supercritical power plant units are the main units in China, andtwo pass type П (type) boilers and tower type boilers are the main boiler types. Today inChina, П type boilers are the overwhelming majority in600MW power plants. In thepaper, the analysis has been made from the engineering design practice data from600to1000MW capacity power plant units home and abroad. The criterion is combined witheconomical rationality, running reliability and practical security. The feasibility problemof the boiler type selection in the forth stage of the project，2×660MW Ultra-supercriticalUnits in Jiujiang Power Plant and the technical economy camparision between П typeboiler and tower type boiler have been studied. This research results have importantdirection and lesson affect for the boiler selection in the same capacity unit.Firstly, the main boiler manufacturers and the technology characteristics of differenttype boiler which size is in600～1000MW coal-firing unit at home and abroad is brieflyanalyzed. According to demand of the fuel characteristics and design parameters, thepreliminary plan of П type boilers and tower type boilers for2×660MW units are made.This includes boiler integrated arrangement, the boiler whole design, start-up system,combustion equipments, air heater, soot blowers, pressure relief valve, steel frameworkand platform stair.Secondly, a full comparison of the design proposal about the two boiler types has beenmade. The main technical characteristics, performance index and the overall economicbenefits have been analyzed. Compare with П type boiler, the main advantages of thetower boiler are the higher boiler efficiency, lower NOx emission, the lower flowresistance both in the flue gas side and water-steam side. The disadvantages of the towerboiler are higher boiler metal consumption, a higher burner resistance and the number ofthe field weld is bigger. Compare with П type boiler, the tower boiler can decrease theamount of the soot discharged568t, SO2emission24.95t and NOx emission9.59t.According to energy-conserving and environment-protective and social effect, tower typeboiler is a better choose for2×660MW units in Jiujiang power plant.Furthemore, from the practical situation point of view, according to heat transfer crisisand over-temperature tube burst owing to thermal deviation and hydrodynamic instability,based on the thermal calculation, the hydrodynamic characteristic of the660MWUltra-supercritical Unit is calculated in use of the former Soviet Union boilerhydrodynamic calculation method. Flow friction characteristic and hydrodynamiccharacteristic in boiler water wall is got and the heat transfer crisis in the boiler water wall has been checked.Thirdly, the tube burst problems because of too many welds in panel existed in thetower type boilers in ultra-supercritical units made by China, which used T23steel as thewater panel and optimizing and impoving welding procedure can insure security operationof the units.Finally, sum up all the factors the tower type boiler is the most suitable one for2×660MW ultra-supercritical units in Jiujiang Power Plant.