Horizontal In-Duct Scrubbing of Sulfur-Dioxide from Flue Gas Exhausts

Abstract

Alcoa has conducted multi-year concept validation, pilot and full-scale demonstration studies to assess the technical feasibility of an energy efficient, horizontal gas-flow, co-current in-duct scrubber. The in-duct scrubber was designed and developed with the aim to significantly reduce capital expenditures and operating costs while providing >90% reduction of SO₂ emissions from aluminum smelters, anode bake furnaces, coke calciners and industrial boiler exhausts.

Pilot scale parametric testing of various spray nozzle types and configurations has been conducted to optimize the final scrubber design using a liquid solution for SO₂ scrubbing. More recently, a full scale commercial unit has been installed and is currently operating with SO₂ removal efficiencies greater than 92%. The scrubber treats the exhaust gases from an anode baking furnace with flows ranging between 120,000 and 150,000 cubic feet per min (cfm), liquid to gas (L/G) ratios ranging from 10–12 gallons/1000 acf (actual cubic feet) and an overall pressure drop across the scrubbing unit at or below 1.5 inch w.g. (water gauge). Future testing of this unit will entail detailed evaluation of the system’s capability in removing fine particulates.