Lower Water Wall Transverse Crack Cause Analysis And Comprehensive Management Of Domestic Ultra-supercritical Vertical Water Wall Boiler

With China's thermal power cause of the rapid development, reduce the energy consumption and pollution has become the urgent matter, the development of supercritical and ultra supercritical thermal power unit is to achieve these two goals is one of the most important ways.Huaneng yingkou power plant phase ? 2 units of 600MW ultra-supercritical boiler as the domestic first batch of the launch of the first and second units,2007 to 2012, huaneng yingkou power plant phase ? 2 sets of boiler water wall running about 30000 hours, water wall during the recent overhaul that local transverse cracks, part of the position of crack depth has reached half of the overall thickness, crack appeared, the specific time and unexplained units due to leakage caused by the crack has frequent downtime, affect the safe operation of unit. Statistical yingkou power plant 2 units and put into operation in October 2012,37 for water wall leakage, leakage down 7 times in half of a year on average for water-cooled wall. In addition to the early stages of the unit operating in foreign body orifice obstruction, the parent metal manufacturing quality questions, is the largest proportion of transverse crack problem. If can effectively control the generation of transverse crack and improve the safety of water wall, decrease The Times of leakage and can bring huge economic benefits for power plants.Water wall tube surface transverse crack in the region of the furnace heat load is higher, the crack development in this side by the outer wall to wall, cracks, macro and micro characteristics are characterized by thermal fatigue crack, crack in this side of the metallographic organization spheroidizing is significantly higher than the back fire side grade 1, indicates that the regional water wall this side slightly overtemperature phenomenon. From the point of metallographic analysis results, the reason of crack is short-term outcome of combined action of moderate temperature alternating.Through field test and parameter test, found in the operation of the unit water wall outlet temperature rapid fluctuations significantly, and overtemperature phenomenon exist in the process of temperature fluctuations. Aiming at the cause of crack, through calculating hydrodynamic distribution, water wall of orifice, water wall temperature distribution in the obvious flatten out, wall temperature along the furnace wall width deviation decrease obviously. Combustion adjustment experiment, improve the combustion conditions, balanced combustion inside the furnace, the control parameters tend to be more reasonable, sharply reduced parameters, rapid fluctuations.Through comprehensive treatment work, the safe operation of the 2 units have been nearly 200 days, not downtime caused by leakage of water wall, wall greatly increased safety. The study has great significance to the unit safe and continuous operation, to provide reference for the safe operation of similar type units.