Process for recycling spent potliner and electric arc furnace dust into commercial products using oxygen enrichment

Abstract

This paper discusses the Enviroscience, Inc (ESI) process for recycling hazardous wastes by extractive metallurgy followed by vitrification of non-reducible metal oxides. In this process, volatile and reducible metals are reclaimed as their respective oxides and elements. Non-reducible metal oxides are converted into a man-made vitreous fiber identical in chemical content to mineral wool fiber known as rock or slag wool. The project discussed here involved aluminum plant and steel plant recycling of potliner and EAF dust into commercial products. Potliner (K088) is produced by primary aluminum plants. The annual waste generation rate is 130,000 tons/year. Electric Arc furnace dust (K061) is produced by 76 steel companies and the annual generation rate is estimated to be 600,000 tons/year. An 18-inch I.D. (pilot plant scale) countercurrent mineral wool type shaft furnace was used in the project. The feed was spent potliner and electric arc furnace dust. The pilot plant results were 1) cyanide consumption as a reductant: 96.89% to 99.55%, 2) fluoride utilization: 69.2% to 89.50%, 3) zinc recovery: 96.54% to 97.76%, 4) cadmium recovery: 99.47% to 99.99%, 5) lead recovery: 97.98% to 99.41%, 6) slag (fiber) recovery: 49.33% to 64.31%, 7) iron recovery: 95.12% to 96.93% in the iron and slag (fiber) products. Oxygen enrichment tests conducted by Airco increased the furnace melt rate by 44.8% and reduced coke consumption (energy use) by 41.4%. No detectable levels of NO 2, N 2O 3, H 2S, SO, or SO 2 were found in limited emissions test. Oxygen enrichment resulted in 66.3% fiber production. Analytical results on the enriched zinc oxide iron and fiber products are comparable to prior tests conducted by Enviroscience. As a result of these tests, extractive metallurgy combined with fiber production (vitrification) has now been proven to be a cost-effective recycle process when compared to thermal treatment, secure landfill disposal or standard HTMR processes. The process provides for the production of commercial products from select inorganic liquid, semi-solid, and solid hazardous wastes.