DEVELOPMENT OF SOLVENT EXTRACTION RIG UNITS FOR SYENSQO’S MAXYIELDTM TECHNOLOGY TO REMOVE ORGANICS FROM BAYER PROCESS

Accumulation of organics in Bayer process liquors has many negative impacts on alumina production, including reduced liquor productivity and precipitation yield, lower quality alumina product, and increased energy consumption. Syensqo’s MAXYIELDTM breakthrough technology, based on solvent extraction (SX), has shown great potential to help alumina refineries significantly reduce the total organic carbon (TOC) in their Bayer liquor, and thus improve their production efficiency. The MAXYIELDTM technology utilizes an extractant, which is not miscible with Bayer liquor, to extract organic anions from Bayer liquor. The treated Bayer liquor with reduced TOC can be sent back to the Bayer process. Following the extraction step, the TOC-loaded extractant goes through a strip and a regeneration step to be purified for recycling. During the development of this technology, bench-scale shake-out tests were first conducted to demonstrate the solvent extraction efficiency. A lab-scale SX rig was then designed and built to examine the performance in an integrated, continuous circuit. The SX rig design was then scaled up to a pilot scale to examine the physical performance of this design prior to the manufacture of a full pilot SX circuit. This paper presents an overview of the development of this technology from bench testing to pilot-scale equipment testing. The SX rig design, test data for MAXYIELDTM, and the effort Syensqo has made toward the commercialization of this technology will be discussed. It has been shown that the three steps (extraction, strip, regeneration) can be continuously operated in the bench scale rig units with stable TOC removal efficiency. It has also been found that agitation during mixing has a significant impact on the entrainment of extractant in aqueous streams.