Recovery of coal fines from preparation plant effluents

Abstract

Objectives of this project are to test and demonstrate the feasibility of recovering the coal fines that are currently disposed of with coal preparation plant effluent streams in order to produce a fine clean coal product that can be blended with the plant coarse clean coal. This recovery will be effected by means of Michigan Technological University's static tube flotation process, which has been successfully demonstrated on a number of raw coals to reject 85% of the pyritic sulfur and recover 90% of the combustible matter. The main activities completed during this period were characterization studies consisting of washability testing and froth and film flotation studies. In addition, the ash and total and pyritic sulfur contents of the sink-float fractions of the four project effluent slurry samples were determined in order to provide an estimate of the liberation of the mineral matter in the test samples. Static tube flotation tests conducted at Michigan Technological University on the effluent samples collected from four operating Illinois preparation plants achieved excellent results. A test on effluent Sample A resulted in a clean coal of 7.5% ash and 1.1% total sulfur at 97.7% Btu recovery. Another test on the same sample aimed at loweringmore » the ash further analyzed at 3.0% ash and 0.92% total sulfur but with lower Btu recovery. Test results on the other samples confirmed that the static tube can be used to recover coal containing low ash and sulfur with high recovery of carbonaceous material from plant waste streams. The static tube test results were compared with the washability analysis of the effluent samples and, in the case of one sample, with best results from conventional froth flotation. The performance of the static tube far exceeded that of conventional flotation and closely approached that of the theoretical limit of separation indicated by the washability tests. 7 figs., 16 tabs.« less