Sulfur Elimination in Updraft Lead Sintering — A Thermochemical Model

Abstract

Experience indicates that sulfur elimination in updraft lead sintering is about 85% complete. Physical chemistry of the Pb-S-O system suggests that poor elimination may be due to sulfate formation at temperatures below about 900/dgC. The following model calculates temperatures in the sinter bed as a function of time and location, and estimates sulfur elimination from the calculated temperature and fraction reacted in each volume element. Effects of several variables are explored: higher ignition fuel, smaller pellets, downdraft operation, decreased excess air, higher concentrate level, moisture in the mix, and grate speed. None of these seemed very effective, for a variety of reasons. But oxygen enrichment did lead to 96.6% calculated sulfur elimination without excessive bed temperatures, using 0.08 kg oxygen per kg new lead in concentrates. The model calculates that concentrate level in the machine feed can be increased by 10% or more by using fog nozzles in those wind boxes above which excessive temperatures are otherwise reached, and by using oxygen where temperatures are too low.