WESP Explosion
Operational mistakes can cause an explosion to occur in the wet electrostatic precipitator (WESP) of an incineration system. Combustible gases build up in the sludge lines when the valves are closed to the incinerator and when opened quickly these gases enter the reactor. Starting the fluidizing air blower then pushes these gases through the heat exchanger, scrubber, and into the WESP. There, the gases are introduced to an induced electrostatic charge, creating an ignition source causing an explosion. As shown, this type of explosion can severely damage tray scrubbers along with ancillary equipment. Initial and observed symptoms:
Analysis Numerous log entries concerning problems with the fuel oil system combined with strip chart evidence of poor/incomplete combustion lead to the ultimate conclusion that an excessive amount of fuel oil was being injected into the incinerator and/or its supporting air systems. Furthermore, a large portion of the fluidizing air was found to be bypassing the furnace and going straight to the stack resulting in higher windbox temperatures and poor fluidization. The main indications of the problem were those of poor or incomplete combustion. There was commonly an extreme depression in the measured levels of oxygen with a corresponding spike in carbon monoxide associated with each alarm or “explosion” event. Indications of the actual explosion type phenomenon are evidenced by a spike in the measured scrubber and venturi differential pressure. These key indications were commonly found during the restart following a brief shutdown period. |
Conclusions
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