Applied Catalysts worked via an agreement with Electric Power Research Institute to develop the EPRICON process to convert SO2 to SO3 to enhance flue gas fly ash removal specifically from a coal fired power plant when the boilers were burning low sulfur coal. The EPRICON process required the development of a fused silica honeycomb support for a vanadium pentoxide (V2O5) catalyst supporting EPRI’s US Patent #5,011,516, issued in April, 1991.
THE EPRICON PROCESS – Coals naturally contain a small percentage of sulfur, which becomes oxides of sulfur (SO2 and SO3) as the coal burns. Electrostatic precipitators (ESPs) are designed into a coal fired boiler’s flue system to remove fly-ash, using the level of SO3 produced during combustion of high (normal level) sulfur coal to condition, or control, the ash’s electrical resistivity so the ESPs are able to efficiently remove fly-ash. If utilities, under regulatory pressure, begin burning low sulfur coal to lessen their emission of oxides of sulfur, the amount of SO3 in the flue gas stream drops, rendering those ESPs ineffective in removing sufficient fly-ash from flue gas to keep stack emissions clear.
When coal is burned in a boiler, most of the sulfur it contains becomes SO2, sulfur dioxide, while a small percentage ends up as SO3, sulfur trioxide, 3% or less of the combined mix of oxides of sulfur. It is the SO3, not the SO2, which is effective in decreasing electrical resistivity of the fly ash so it can be removed from the flue gas by an ESP. Generally, older ESPs were originally designed to operate properly with the levels of SO3 coming from combustion of high sulfur eastern coals (1%+). Coal blends containing less than 1% sulfur produce less SO3 than required for proper ESP operation, resulting in boiler capacity limitations (de-rating) due to excessive stack fly ash emissions (opacity). In correction, EPRICON systems are used to convert (oxidize) a large portion of the unusable SO2 into usable SO3 in a small diverted side stream (slip stream) of boiler flue gas, which is then re-introduced into the main flue gas stream upstream of the ESP to raise the overall SO3 content of the flue gas stream back to design level, thereby producing a decrease in fly ash resistivity in the flue gas stream.
Contact Applied Catalysts regarding questions about the EPRICON process.