Regeneration of spent bleaching earth by Lye-extraction

Lye extraction was investigated for regenerating a spent bleaching earth (SBE) generated after the discoloration of crude edible oils. Bivariate regression and response surface methodology were applied to find the optimal ratio of the liquid caustic soda to SBE and the retention time at the boiling temperature. Experimental results showed that the oil content in SBE could be reduced to less than 196 by boiling SBE in an aqueous solution of 19,6 caustic soda for more than 20 min. The deoiled SBE could be mixed in the soy meal for animal feed. A preliminary financial analysis showed that the investment for a hypothetical 10-ton/day processing unit and an additional 50-ton/day acidulation and a 100-ton/day wastewater treatment unit would be paid back in 24 months. The contour lines of the payback period between 18 and 36 months for the investment between $400,000 and $1,200,000 and the meal price between $200 and $300/ton are also shown. (c) 2006 American Institute of Chemical Engineers Environ Prog, 25: 373-378, 2006.