Pilot scale-SO2 control by dry sodium bicarbonate injection and an electrostatic precipitator

A 500 actual cubic feet gas per minute (acfm) pilot-scale SO(2) control study was undertaken to investigate flue gas desulfurization (FGD) by dry sodium sorbents in 400 degrees F (204.5 degrees C) flue gases emitted from a coal fired boiler with flue gas concentrations between 350 and 2500 ppm SO(2). Powdered sodium alkaline reagents were injected into the hot flue gas downstream of the air preheater and the spent reagents were collected using an electrostatic precipitator. Three different sorbents were used: processed sodium bicarbonate of two particle sizes; solution mined sodium bicarbonate, and processed sodium sesquicarbonate. SO(2) concentrations were measured upstream of the reagent injection, 25-ft (7.62 m) downstream of the injection point, and downstream of the electrostatic precipitator. SO(2) collection efficiencies ranged from 40 to 80% using sodium bicarbonate stoichiometric ratios from 0.5 to 3.0. Much of the in-duct SO(2) removal occurred during the first second of reagent reaction time, indicating that the sulfur dioxide-sodium reaction rates may be faster than have been measured for fixed bed measurements reported in the literature. (C) 2007 American Institute of Chemical Engineers Environ Prog.