WESPGUARD 7110

Wet Electrostatic Precipitators (WESPs) use electrically charged plates or tubes to remove small wood particles, fly ash and organic material from hot gases that are produced during the process of drying wood particles, chips, pellets or veneers.  Without treatment, the plates or tubes become fouled, resulting in a decrease in efficiency.  This decrease in efficiency allows wood particles and organic contaminants to escape up the stack.

Traditionally straight commodity Caustic Soda has been used for treatment, however treating a WESP with Caustic Soda contributes significant additional system operation and maintenance costs.  Caustic soda cleans adsorbed organics on the tubes or plates through a process called saponification and also serves to remove small attracted wood particles from the surface of the WESP.  The problem is that the products of saponification (soap) will react with any level of hardness present in the water to form large amounts of insoluble lime soaps (similar to soap scum) and mineral scales (calcium carbonate).  Buildup of these deposits over time can lead to flow reduction or plugging of piping and nozzles resulting in costly system shutdowns to acidize and remove the scale.  In addition, Caustic Soda is manufactured through the electrolysis of sodium chloride and often contains a high concentration of chlorides.  Chlorides at low concentrations have the potential to increase the risk of corrosion to stainless and mild carbon steel components.  In systems where the water is recycled, the chloride concentrations can cycle up and over time create extremely corrosive environments.

Not only does caustic soda affect the components of the WESP, but it also has the potential to have a significant impact on the operation of the Regenerative Thermal Oxidizer (RTO) which is utilized after the WESP to further treat exhaust gases.  Carryover of the caustic has the ability to form a glaze on the ceramic media contained within the RTO reducing its efficiency and resulting in increased cost of operation.  In addition, at the high temperatures the RTO operates at caustic exhibits the ability to attack ceramics, causing pitting, drastic mass and bending strength loss and ultimately reducing the lifespan of the ceramic media.