AN EXPERIMENTAL STUDY OF THE TREATMENT OF ALUMINUM-CELL GASES FOR POLLUTION CONTROL USING FLUIDIZED-BED TECHNOLOGY

Abstract

This paper describes the two-stage treatment of tars and hydrogen fluoride contained in emitted aluminum-cell gases for pollution control and recovery of useful components. The treatment involves combustion of tar and then chemisorption of hydrogen fluoride on alumina particles in a fluidized-bed reactor of 25 cm inner diameter. Calcined coke was used to support the combustion of tar. Smelter-grade alumina was used as the bed material with average particle size of 66.71 μm. Stability and temperature uniformity of the bed were confirmed for different operating conditions. The tar was removed with combustion efficiency of up to 98% at a bed temperature of 700–900°C. Heat removal from the bed by water cooling tubes was achieved with a heat transfer coefficient as high as 450 W/m² · K. The hydrogen fluoride was captured by chemisorption with a scrubbing index of up to 0.75 kg⁻¹ depending on the bed temperature, distributor design, fluidizing velocity, and bed height. Good reactor performance could be obtained with a distributor fitted with 113 nozzles each having six inclined holes.

Keywords:

• Aluminum cell
• Chemisorption
• Combustion
• Environment
• Fluidized bed

Acknowledgments