Lignite cleaning in NaCl solutions by the reverse flotation technique

A cleaning possibility of low (BD) and high ash content (IM) lignites in NaCl solutions using a reverse flotation technique was studied. Preliminary test results indicated that BD lignite cannot be cleaned effectively in the traditional manner because gangue was floated first rather than a combustible material. Further studies indicated that the lignite cleaning in NaCl solutions using the reverse flotation technique is possible. However, a large quantity of dodecyl amine hydrochloride (DAH) was required. A lower ash content in a concentrate can be obtained by addition of NaCl. A concentrate yield can be im-proved by addition of starch. Under the test conditions, for BD lignite with the ash content in the feed 15.19%, the ash content in the concentrate 11.44% and the concentrate yield 67.38% were obtained. Similarly, for IM lignite with the ash content in the feed 57.40%, the ash content in the concentrate 32.90% and the concentrate yield 25.08% were obtained. The flotation rate constant k and maximum ash recovery ε∞ significantly increased with the NaCl concentration.