TECHNOLOGIES

ClearGas™

ClearStack Combustion Corporation has developed a dry scrubber technique called ClearGas™ that uses potassium hydroxide (KOH) to reduce sulfur oxides and nitrogen oxides from flue gases by 70 to 90%. It will also remove sulfur trioxide (SO3) that will reduce flue gas opacity.

Aqueous potassium hydroxide (KOH) is spray dried into the flue gas using in-duct injection or a dry scrubber. The KOH reacts with SO2 to form K2SO4 and reacts with NO and NO2 to form KNO3, both salts of which are captured and removed with the fly ash from a downstream electrostatic precipitator (ESP) or baghouse. The presence of potassium salts in an ESP, decrease the resistivity and increases the "spark over" voltage to improve particulate removal performance even though SO3, a fly ash conditioning agent, is removed in the process.

The process produces a byproduct of salable potassium nitrate, potassium sulfate-fly ash fertilizer.

Economics show that this dry scrubber technology is a low cost technique to bring small coal-fired stokers into environmental compliance. It is less costly than a stoker replacement with a natural gasfired boiler system or a conversion to coal-fired fluidized bed combustion systems. It also can be used as an SO2/NOX trim technology for large coal-fired electric utility boilers.