Chromium Recovery from High-Temperature Shift Cr-Fe Catalysts (With an Appendix on Process Economics)

摘要

The Bureau of Mines has devised a procedure to selectively extract and recover chromic oxide (Cr2O3) from waste high-temperature shift catalysts that contain approximately 6 pct Cr and 62 pct Fe, both in oxide form. The Bureau's procedure consists of roasting the waste catalyst with sodium hydroxide (NaOH) or sodium carbonate (Na2CO3) followed by water leaching. The chromium from the leach liquor was recovered utilizing an oxidation-reduction reaction with pH adjustment to form a hydrous chromic oxide (Cr2O3XH2O) precipitate. The roast-leach procedure produced chromium extractions greater than 89.7 pct, with product recovery in excess of 99 pct from the leach liquor. The costs of the NaOH and Na2CO3 roast processes, including sizing and equipment-related recommendations, were determined by the Bureau's Office of Process Evaluation. The economic evaluation indicates that producing a Cr2O3 product, at the present time, is not competitive with the present-day cost of imported chromites. The estimated average operating cost for both processes was $5.44/lb of recovered Cr2O3 concentrate. However, the procedure offers a potential alternative to the disposal of the waste through landfill.