Catalytic process for decolorizing yellow plume

Abstract

Yellow-colored exhaust gas streams from internal engines or gas turbines, frequently referred to as “yellow plume,” contain nitrogen dioxide (NO₂) at concentrations as low as 15 ppm. The process developed in this work for decolorizing the yellow plume is based on reduction of NO₂ to NO utilizing a combination of a Pt catalyst and a reducing agent. A stoichiometric excess of carbon monoxide, diesel oil, methanol or ethanol were used as reducing agents. Depending on the type of the reductant, the active temperature window of NO₂ reduction was varied with methanol and CO being active at lower temperatures and ethanol and diesel oil at higher temperatures. By changing the Pt loading of the catalysts the active temperature window of NO₂ reduction was also changed, higher loading Pt catalysts being active at lower temperatures. This scheme of NO₂ reduction process was verified in a pilot-scale test with the real exhaust gas from the gas turbine power plant, showing 96% of NO₂ reduction at the stack temperatures of 102–123 °C and at space velocities of 28,000–95,000 h⁻¹ with inherent CO in the exhaust gas as the reducing agent.