An aggressive form of corrosion has been found in（积极的腐蚀形式被发现）.pdfVIP

tate-of-the-art flue gas desulfuriza- The STory in Brief tion (FGD) systems have been and Sare being installed in most coal- An aggressive form of corrosion has been found in fired electric generating units in the United relatively new flue gas desulfurization systems States to meet regulatory emission require- ments for control of sulfur dioxide (SO ). 2 installed in U.S. coal-fired plants. In response, EPRI These systems are capable of removing 95% or more of the SO in the flue gases. has launched a rapid-response project to investigate 2 However, in the past year, utilities have the root cause of the corrosion and to develop been confronted with a troubling trend. Some of the newer wet FGD units have inspection and mitigation methods. experienced severe corrosion in just three years, and in extreme cases, in as little as three months. corrosion can be significant. Mitigation accelerated corrosion. Generally, FGD sys- The corrosion most commonly is found measures––even temporary stopgap mea- tems include wet scrubbers, spray dryers, below the liquid level in the FGD absorber sures––have been reported to cost as much and dry sorbent injection systems. The cor- vessels and piping. It first appears as pitting as $8 million. Outages to address the issue rosion in question has been found only in in weld heat-affected zones, weld metal, typically are unplanned, and it can take wet scrubbers, which typically remove SO2 and base metal and most often is associated weeks to clean, inspect, and repair vessels. from the flue g