2010 Volume 59 Issue 12 Pages 456-463
Recently, a pulverized coal firing boiler is getting large capability; therefore, it should take a further effective environmental measure. As a facility aspect, it takes a measure to inhibit the amount of generation of NOx and, in operation aspect; it is operated by low O2 combustion. As a result, in the combustion chamber, it becomes to low O2 atmosphere because of lack of oxygen and also the sulfide corrosion becomes actualized because of H2S. In addition to that, it is recognized that it accelerates damages by multiple influences from erosion damage by steam blast from the wall blower to remove slag. The damage behavior around wall blower in the investigated boiler is as follows. (1) Steam erosion by direct collision of high temperature and high pressure steam. (2) The coal ash that was caught in the current of steam injection and collided on the tube surface causes the ash erosion. (3) The steam that is lower temperature than the tube temperature collides onto the tube surface which is exposed by high temperature combustion gas and that causes the thermal collision. The synergistic result of those 3 physical collisions causes a crack and delamination in the scale. Moreover, because of the above results, when the nascent metal aspect is exposed it is directly contacted with combustion gas. And that prompts the high temperature corrosion response and it is accumulated. For that result, it was concluded that the damage has been accelerated.