Pilot-Scale Demonstration of the OSCAR Process for High-Temperature Multipollutant Control of Coal Combustion Flue Gas, Using Carbonated Fly Ash and Mesoporous Calcium Carbonate

Abstract

A pilot-scale study of the Ohio State Carbonation Ash Reactivation (OSCAR) process was performed to demonstrate the reactivity of two novel calcium-based sorbents toward sulfur and trace heavy metal (arsenic, selenium, and mercury) capture in the furnace sorbent injection (FSI) mode on a 0.365 m3/s slipstream of a bituminous coal-fired stoker boiler. The sorbents were synthesized by bubbling CO2 to precipitate calcium carbonate (a) from the unreacted calcium present in the lime spray dryer ash and (b) from calcium hydroxide slurry that contained a negatively charged dispersant. The heterogeneous reaction between these sorbents and SO2 gas occurred under entrained flow conditions by injecting fine sorbent powders into the flue gas slipstream. The reacted sorbents were captured either in a hot cyclone (∼650 °C) or in the relatively cooler downstream baghouse (∼230 °C). The baghouse samples indicated ∼90% toward sulfation and captured arsenic, selenium and mercury to 800 ppmw, 175 ppmw and 3.6 ppmw, respectively.