Industrial Application of the Flushing Process to High Purification of Natural Raw Materials

The flushing process was developed by the author for the purpose of highly efficient separation of fine impurity particles from ceramic raw materials. In this sophisticated process, ultrafine mineral particles of under 1mum size suspended in raw ore slurries are extracted with kerosene. In this report, a natural amorphous graphite and some sericite clays were treated experimentally using a commercial liquid-liquid continuous extraction apparatus to reveal the practical value of the flushing process in industrial application. The amorphous graphite which was already concentrated in China was selected for the further elimination of clayy impurities. The sericite clay occurring at Taiwan is sometimes required to lower the contents of As and Pb for the use in cosmetics. The low grade sericite occurring at Okayama contains abundant pyrite for which the separation of pyrite is necessary for its industrial application. These raw materials were classified at a certain size of micrometer order in prior to the flushing operation. The aqueous slurries were conditioned at pH 4.3 in the presence of citric acid, EDTA,sodium dithionite to enhance the hydrophobicity of desired substance for oil-extraction. Besides operational conditions were determined such as feed rate, numbers of oscillating motion of impeller, slurry density, hold-up fraction. The commercial extractor made by Shimasaki Manufacturing Co.showed excellent function for the oil-extraction of solid particles owing to its cylinder-shaped impeller by which high shearing stress fine oil droplets are created available for the collection of the hydrophobic solid particles, together with the release of the constituent particles to individual particles. The graphite particles extracted into the oil phase were returned to its original aqueous dispersions by the addition of nonionic surfactant and sodium carbonate and were recovered using centrifuge. The ash content of the 2mum sample was significantly lowered to 1.8mass% with the removed ratio of 88.5%. In addition, the waste oil was regenerated by washing with sulfuric acid. Separation of pyrite from the sericite clays was well performed. The content of As and Pb in Taiwan sericite could be lowered under the values of criterion for cosmetics. As to Okayama sericite, the efficiency of eliminating Pb was decreased when the raw ore had been oxidized. In conclusion, the experimental results suggest that the flushing process is very advantage for technical purification of natural raw materials.