Teeter bed separation applications.
Elutriators or commonly known as Teetered Bed Separators (TBS) consist of a column with water being introduced at the base (known as teeter water), which rises up the elutriator at a constant velocity. Mineral particles are separated according to their density and size. Particles with a settling velocity less than the velocity of the teeter water will report to the overflow stream, while those with a higher velocity will sink to the underflow. Finer and lower density particles report to the overflow whereas coarser, denser particles report to the underflow. In commercial mineral processing by gravity concentration, the intermediate size range (-2mm+ 75 ,LIm) has not been effecti vel y processed due to industries lack in knowledge of equipment that are capable of effectively beneficiating this size material. This project involved testing the effectiveness of the elutriator with regards to fines beneficiation as well as the development of a prototype unit. Regarding coal (-2.0+ 1.0mm), the Eriez Crossflow unit produced the best results with an E.p. of 0.095, Dso of 1.52 and a product ash content of 8.3%. For the -1.0+ 0.5mm fraction the Eriez Crossflow elutriator was also utilized yielding best results at an E.p. of 0.06, Dso of 1.6 and ash content of 9.1 % (feed ash content of 22.7%). Regarding ferrochrome ore (-2.0+ 1.0mm), no noticeable separation occurred using the Eriez Crossflow unit. For the -1.0+ 0.5mm fraction the Linatex elutriator performed the best yielding an E.p. of 0.085, Dso of 3.18 and a FeCr grade of 85.1 % (feed grade of 28.1 %). For this size fraction the Eriez unit only upgraded the FeCr to 39.6% Regarding hematite ore (-2.0+ 1.0mm), the Linatex unit produced the best results at an E.p. of 0.15, D50 of 3.4 and a Fe grade of 46.7% (feed grade of 32.4%). For the -1.0+ 0.5mm fraction the Linatex elutriator was also utilized yielding best results at an E.p. of 0.45, D50 of 3.75 and a Fe grade of 57.9% (feed grade of 32.4%). The efficiency of separation with regards to different ore types was noticed to be partially dependent upon the feed point to the column. Lighter material was observed to separate more effectively with a tangential feed entry and denser material being separated more effectively with an entry point above the bed. Test work on a prototype unit constructed was conducted using the -1.0+ 0.5mm ferrochrome material. This unit performed well compared with both the Eriez unit and the Linatex unit obtaining an E.p. of 0.075 as opposed to E.p. values of 0.085. The FeCr material was upgraded from 28.1 % to 76.4% with the prototype unit. A continuous two day run undertaken revealed that the elutriator is capable of operating at steady state for a period of time without loss of efficiency.