Research On The Cause Of Fireside Waterwall's Oxide Scales In A Supercritical Boiler

As the development of power plant boiler toward large capacity and high parameter, the pressure and temperature are further improved in China. And boiler waterwall operating environment is very bad, during the operating some accidents usually happen such as over-temperature oxidation, corrosion and even squib. It is also been found in investigation that the same type boiler has the same waterwall oxidation problem in several power plants. So it plays a very great significance that researching the cause and solution of supercritical boilers waterwall oxidation.In this paper, to aim at the oxidation phenomenon of a supercritical boiler waterwall burner region, checked the appearance of oxidation macroscopically, sampled oxidation and analyzed by XRD. Then analyzed the mechanism of waterwall tube failure, in connection with air dynamic field and furnace flue gas temperature measurement experiment, a preliminary judge was that the oxide scales were caused by Over-temperature oxidation, and proposed the solutions of reducing on both sides output of the wall burner.In order to verify the above analysis correctness, firstly carried out furnace sectional thermal calculation, the exit flue gas temperature of each section along furnace height direction and wall radiation heat load distribution characteristics were obtained. On this basis, waterwall temperature calculation was carried out. Acquired the highest region of wall temperature, and determined the risk region of water wall over-temperature easy. Next, made the numerical simulation of furnace combustion to waterwall over-temperature oxygen effect in BMCR condition, researched furnace velocity field, temperature field, gas composition distribution, coal particle trajectories and the rule of wall radiant heat flux density. The results showed that the coal particle movement had the possibility of scouring the side wall, and the furnace burner area was the high heat load areas, especially the high temperature combustion zone of the region is nearer to the side wall.This paper show that furnace combustion heat load too high is the main factor of waterwall high temperature failure, because heat load too high would easily cause waterwall tube temperature too high. Therefore, it is very important that reasonable organization furnace combustion for the safe operation of waterwall.